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Transistor amplifier 05

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Transistor as an amplifier


Aprll 29, slw o 3,, This invention relates to an inter-stage coupling circuit for neutralizing the effects of internal feedback within the semiconductor device used in transistor amplifier circuits. The need for neutralizing the effects of internal feedback within the semiconductor device used in transistor amplifier circuits is well recognized in the prior art. Whether the transistor amplifier is tuned or not, the fact is that the inter-electrode capacitance of the transistor included within the amplifier-more particularly, the collector-base inter-electrode capacitancehas a tendency to introduce unwanted feedback signals from the output circuit into the input circuit.

The above problems are especially acute in multistage, tuned transistor amplifier circuits, such as are found in the picture I. If no neutralization is there provided, then even a slight mistuning in one of the stages can cause it to oscillate, and, by stray feedback, can cause oscillations to break out in all of the stages of the amplifier.

These changes may not be tolerable and if not, like the oscillations, must be compensated for. A number of circuit arrangements have therefore been devised to neutralize the effects brought about by this collector-base inter-electrode capacitance.

Each of these circuit arrangements, by and large, operates to feed back a voltage from the output of the transistor amplifier device to the input such that at the input, the voltage is equal in magnitude but opposite in phase to the feedback voltage through the inter-electrode capacitance. The neutralizing feedback energy then cancels the feedback energy transferred directly between electrodes of the transistor.

One such arrangement employs a series capacitorresistor network connected between the output electrode of the amplifier transistor and the primary coil of the input transformer. A second arrangement employs a series capacitor-resistor network connected between an output winding of the amplifier and the secondary coil of the input transformer. A third arrangement employs a series capacitor-resistor network connected between the output and input electrodes of the transistor.

It will be evident that each of these three circuit arrangements, as well as most others known in the prior art, uses a feedback capacitor to effect neutralization. In some arrangements, a small capacitor is sufficientrln other arrangements a large capacitor is required.

In many arrangements, the capacitor is variable or, if fixed, is shunted by a variable trimmer capacitor, so as to be usable to its fullest extent with transistors having a relatively wide variation in collector-base inter-electrode capacitance from one to another.

These capacitors, Whether small, large, fixed, variable, or shunted represent increased cost to the individual transistor amplifier stage. It is an object of the present invention, therefore, to provide a neutralizing arrangement for a'transistor amplifier circuit which eliminates the need altogether for the heretofore used feedback capacitor. It is another object of the invention to provide such a neutralizing arrangement without adding any off-setting cost to that saved by the elimination of that capacitor.

It is an additional object of the invention to provide such an arrangement which insures stability of amplifier operation even though the transistors employed may exhibit a relatively wide variation in inter-electrode capacitance from one to another. As will become clear hereinafter this is accomplished by the use of a novel type of coupling circuit arrangement, which, in effect, acts as an impedance transformer device between the preceding transistor stage and the next succeeding transistor stage.

For a better understanding of the present invention, together with other and further objects thereof, reference is to be had to the following description taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims. FIGURE 1 shows a schematic diagram of a transistor amplifier circuit including an inter-stage coupling circuit constructed in accordance with a particular form of the present invention;. FIGURE 2 shows a transistor amplifier circuit including a modified form of inter-stage coupling circuit in accordance with the invention;.

FIGURE 3 shows a schematic diagram of an unneutralized transistor amplifier circuit including an interstage coupling circuit commonly employed in the prior art; and. FIGURES 4a and show the amplitude and phase characteristics respectively of the internal feedback voltage as a function of frequency in the transistor amplifier circuits of FIGURES , inclusive, none of which employ the customary feedback capacitor.

The base electrode 14 is connected via a coupling capacitor 18 to the output of a first detector included in the television tuner and represented by the terminal , while the emitter electrode 12 is connected through a conventional emitter resistor 20 and shunt-connected by-pass capacitor 22 to ground.

Capacitor 30 and inductor 32 are serially connected between the base electrode 14 and ground to form a series tuned trap resonant at An inter-stage coupling circuit 34 is connected to the collector electrode 16 of transistor Coupling circuit 34 includes a capacitor 36, an inductor 38, and a resistor One side of capacitor 36 is connected to the collector electrode The other side of capacitor 36 is connected to the positive conductor 28, though in an alternative arrangement, it may be connected to ground instead.

One end of inductor 38 is connected to the junction of capacitor 36 and the collector electrode 16, while the other end is connected to one end of the resistor The other end of resistor 40 is also connected to the conductor Inductor 38 is shown as being variable so as to tune the coupling circuit 34 to the video intermediate frequency, for example, It will be readily apparent that as an alternative, inductor 38 may be of a fixed value and capacitor 36 made variable in order to tune the circuit 34 to this frequency.

Viewed from the collector electrode 16 of transistor 10, the inter-stage coupling circuit 34 appears as a parallel-resonant circuit. A second I. This stage includes a transistor 50 having emitter, base, and collector electrodes 52, 54, and 56, respectively. The base electrode 54 is connected via a coupling capacitor 58 to the junction of inductor 38 and resistor 40, while the emitter electrode 52 is connected through an emitter resistor 60 to ground.

The emitter electrode 52 is also connected through a by-pass capacitor 62 to the positive conductor The capacitor 68 and the conductor 70 are intended to represent the beginning of a second inter-stage coupling circuit connected between the collector electrode 56 and the third I.

It will be understood that this coupling circuit may be similar to the coupling circuit 34 connected to the collector electrode 16 of transistor Although shown as being of a fixed value, capacitor 68 may be variable, instead of the inductor of the second coupling circuit, as was previously mentioned.

Viewed from the base electrode 54 of transistor 50, the inter-stage coupling circuit 34 appears as a series-resonant circuit. In the operation of the tuned transistor amplifier of FIGURE 1, it has been found that as the value of the resistor 40 included within the inter-stage coupling circuit 34 is decreased, the ratio of the inter-electrode feedback voltage to the input voltage to the transistor also decreases.

It has also been found that if the value of the resistor 40 is chosen to be at least several times less than the input reactance of the following transistor stage, this ratio can be made to approximate zero. How close the ratio ultimately comes to zero depends upon the resistance losses within the stage itselfthe less the resistance losses, the closer to zero the ratio comes, But even if the resist-. The extent to which this ratio of feedback voltage to input voltage in the arrangement of FIGURE 1 is less than the ratio in FIGURE 3 type arrangements is such that problems involving stability of amplifier operation are substantially eliminated.

It has further been found that with such a choice of resistance value, this neutralization is only slightly affected by the differences that exist in the inter-electrode capacitances between the different transistors of the same type classification that may be used in the arrangement. With resistor 40 chosen to be of a value equal to 18 ohms, approximately ten times less than the ohms input reactance of transistor 50 at the LF.

In the configuration of FIGURE 2, and more particularly, in the inter-stage coupling circuit 80, one end of an inductor 82 is connected to the collector electrode 16 of transistor The other end is connected to the positive potential conductor 28, though in an alternative arrangement, it may be connected to ground instead.

One side of a capacitor 84 is connected to the junction of inductor 82 and the collector electrode 16, while the other side is connected to one end of a resistor That end is also connected via coupling capacitor 58 to the base electrode 54 of the second I.

The other end of resistor 86 is connected to the positive conductor As in FIGURE 1, inductor 82 is shown as the variable tuning component though it will be appreciated that tuning may be effected by varying capacitor 84 instead.

The inductor 88 and the conductor 90 in FIGURE 2 are intended to represent the beginnings of the next inter-stage coupling circuit. Thus, by choosing resistor 86 to be at least several times less in value than the input reactance of transistor 50 at the operating IF.

FIGURE 4 a shows the amplitude characteristics of the internal feedback voltage of the transistor amplifier stage relative to the input voltage, measured along the ordinate, as a function of frequency, measured along the abscissa, for the configurations of FIGURES l C represents the amplifier characteristic for the same amplifier configurations in the presence of stray resistance loss.

It will be apparent from these three curves that at the tuned resonant frequency, the video intermediate frequency, neutralization has already been effected in the FIGURE 1 and FIGURE 2 configurations dashed-line curve B and dotted-line curve C , whereas some neutralization scheme must be added to the FIGURE 3 configuration solid-line curve A in order to prevent it from becoming unstable in its operation.

Amplitude characteristics B and C are represented as shown because of the impedance characteristics of the interstage coupling circuit Viewed from the base electrode 54 of transistor '50, the coupling circuit 34 appears as a short circuit at the resonant frequency w and as some complex impedance at other frequencies where capacitor 36 and inductor 38 effectively shunt resistor FIGURE 4 b shows the phase characteristics of the feedback voltage of the transistor amplifier stage relative to the input voltage, measured along the ordinate, as a function of frequency, measured along the abscissa, for the configurations of FIGURES These phase characteristics can be used to further illustrate the self-neutralization feature of the present invention.

As shown in FIGURE 4 b , the feedback voltage for the prior art configuration at this frequency is directly in phase with the input voltage phase characteristic A. This is the condition at which the feedback voltage will have its greatest effect on amplifier operation. As is also shown in FIGURE 4 b , however, the feedback voltages at this same frequency for the configurations constructed according to this invention are shifted approximately 90 out of phase with respect to the input voltage phase characteristics B and C.

It will be readily apparent that such a phase shift significantly reduces the effect that the given feedback voltage will have on the operations of the transistor amplifier configuration. As is well known and understood, these variations in gain, as well as the accompanying changes 1n bandwidth, can not be tolerated in a video I.

In the transistor I. The empedance transformation which they establish between I. Thus, adjustment of different values for the inter-stage coupling resistor will not only provide the requisite feedback neutralization, but will also provide the desired impedance transformation to stabilize the amplifier gain and bandwidth.

It will be obvious to those skilled in the art that, while the present invention has been described as it would be used within the video I. It will be equally obvious that while NPN transistors have been used in the two embodiments of the invention disclosed, and used in the common-emitter coinfigurations, neither is to be construed as a limiting factor of the invention.

Various changes and modifications may be made in these, and other, respects without departing from the true spirit and scope of the invention.

An amplifier circuit comprising:. An amplifier circuit according to claim 2 in which said first reactive component is a capacitor and said second reactive component is an inductor.

An amplifier circuit according to claim 2 in which said first reactive component is an inductor and said second reactive component is a capacitor. An amplifier circuit according to claim 2 in which said first and second transistors are connected in a common emitter configuration. An amplifier circuit according to claim 2 for use in the video intermediate frequency portion of a television receiver in which said first reactive component is tuned with respect to said second reactive component to provide maximum application for signals having a frequency equal to the intermediate frequency of said video portion and in which the value of said resistive component is substantially less than the reactance of said second transistor at said intermediate frequency.

An amplifier circuit according to claim 2 in which said feedback signal is efiectively short circuited to ground through said parallel-resonant circuit at the resonant frequency thereof. An amplifier circuit as defined in claim 2 wherein said first source and said second source are of substantially the same uni-directional potential value. USA true Inter-stage coupling circuit for neutralizing internal feedback in transistor amplifiers.

USA en. ATB en. BEA en. BRD0 en. DEB2 en. DKC en. ESA1 en. FIC en. GBA en. NLB en. NOB en. SEB en. Very high frequency tuner for eliminating image interference and stray capacitance effects.


Semiconductor: MPSU05 (MPSU 05) - NPN SILICON AMPLIFIER TRANSISTOR...

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Bitar 10/05/ Transistor Amplifiers. Small Signal Modeling Examples. 3. Common Emitter Amplifier w/ Voltage Divider Bias & Emitter Bypass Capacitor.

MMSTA-05 SMT NPN Transistor


If you open up the perennial favourite electronics textbook The Art Of Electronics and turn to the section on transistors, you will see a little cartoon. If you apply a little more base current, he pushes up the collector a bit. If you wind back the base current, he drops it back. Of course the base-emitter junction is a diode and it is not a simple potentiometer that sits between collector and emitter. Fortunately it is possible to work with transistors without such an in-depth understanding of their operation, but before selecting the components surrounding a device it is still necessary to go a little way beyond transistor man. Imagine for a moment a simple transistor circuit involving a single NPN transistor with its emitter grounded, its collector tied to the positive supply by a resistor, and a potentiometer between ground and supply allowing any voltage to be supplied to the base. Because the emitter is grounded, even if sometimes via a resistor, this transistor configuration is referred to as a Common Emitter amplifier. In this circuit if you were to start with the potentiometer at the grounded end then the transistor would be turned off, and no current would flow.

Transistor as an Amplifier

transistor amplifier 05

Research , Volume: 15 1 DOI: Citation: Pandya KV. Biotechnol Ind J. Enough research has been carried out till date based on conventional solid state electronic circuits.

For any questions about price, specific products, comments on Lab-Volt products or if you have any issue regarding Lab-Volt products, please contact us using the following email addresses :. The Transistor Power Amplifiers module is designed to teach troubleshooting of transistor power amplifier circuitry.

Tube sound


Aprll 29, slw o 3,, This invention relates to an inter-stage coupling circuit for neutralizing the effects of internal feedback within the semiconductor device used in transistor amplifier circuits. The need for neutralizing the effects of internal feedback within the semiconductor device used in transistor amplifier circuits is well recognized in the prior art. Whether the transistor amplifier is tuned or not, the fact is that the inter-electrode capacitance of the transistor included within the amplifier-more particularly, the collector-base inter-electrode capacitancehas a tendency to introduce unwanted feedback signals from the output circuit into the input circuit. The above problems are especially acute in multistage, tuned transistor amplifier circuits, such as are found in the picture I.

X5 MPSA05, 60V 0.5A, NPN Transistor Amplifier Amp, TO-92, ^

Figure below. It is called the common-emitter configuration because ignoring the power supply battery both the signal source and the load share the emitter lead as a common connection point shown in Figure below. This is not the only way in which a transistor may be used as an amplifier, as we will see in later sections of this chapter. Common-emitter amplifier: The input and output signals both share a connection to the emitter. Before, a small solar cell current saturated a transistor, illuminating a lamp. When there is just a little light shone on the solar cell, the lamp will glow dimly. Suppose that we were interested in using the solar cell as a light intensity instrument. We want to measure the intensity of incident light with the solar cell by using its output current to drive a meter movement.

Report Date: Pagination or Media Count: Abstract: NPN double-diffused silicon microwave transistors were fabricated using.

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Tardigrade Question Physics Consider an n-p-n transistor amplifier in common emitter configuration. The current gain of the transistor is If the collector current changes by 1 mA, what will be the change in emitter current? Get Android App.

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Tube sound or valve sound is the characteristic sound associated with a vacuum tube amplifier valve amplifier in British English , a vacuum tube -based audio amplifier. After introduction of solid state amplifiers, tube sound appeared as the logical complement of transistor sound, which had some negative connotations due to crossover distortion in early transistor amplifiers. Thus the tube sound now means 'euphonic distortion. Many electric guitar , electric bass , and keyboard players in several genres also prefer the sound of tube instrument amplifiers or preamplifiers. Tube amplifiers are also preferred by some listeners for stereo systems. Before the commercial introduction of transistors in the s, electronic amplifiers used vacuum tubes known in the United Kingdom as "valves".

Vallese, New York, N. This invention relates to transistor amplifiers and especially to unilateralized transistor amplifiers. Unilateralization of transistor amplifiers design of transistor amplifiers for unidirectional amplification of energy has until now been accomplished by the use of transformers or the use of bridge compensating networks at the input or output terminals.




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  1. Voodooran

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