Video amplifier transistor circuits

Simon Ndiritu from General Dielectrics explains some basic capacitor selection guide for coupling and decoupling applications. Capacitors are fundamental components in both analog and digital electronic circuits. These passive components play an important role in influencing the operational behavior of circuits. The characteristics of a capacitor vary mainly depending on the dielectric material used. The dielectric material determines the capacitance value, energy efficiency, and size of a capacitor.

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Content:

• Principles of Transistor Circuits
• Simple two transistor amplifier
• Capacitor Selection for Coupling and Decoupling Applications
• Video Amplifiers
• Simple Video Amplifier
• US2921196A - Transistor regenerative detector circuit - Google Patents
• transistor amplifier Circuit Using BC547 Transistors
• Subscribe to RSS
• Multi-Stage Transistor Amplifier
• Different Types and Applications of Amplifiers

WATCH RELATED VIDEO: Transistor Amplifiers - Class A, AB, B, \u0026 C Circuits

Principles of Transistor Circuits

The common-emitter amplifier also known as the common-earth or grounded-emitter circuit has a medium value of input impedance and provides substantial voltage gain between input and output. The common-emitter amplifier can be used in a wide variety of digital and analog voltage amplifier applications. When the input is zero, the transistor is cut off and the output is at full positive supply rail value.

When the input is high, the transistor is biased on and a collector current flows via R L , thus pulling the output low. Thus, the output signal is an amplified and inverted version of the input signal. In Figure 1 , resistor R b limits the input base-drive current to a safe value. In practice, R b should be as small as possible, consistent with safety and input-impedance requirements, and must not exceed R L x h fe.

Q1 switches fully on, with its output a few hundred mV below the positive supply value, when the input is at zero volts, and turns off with its output at zero volts when the input rises to within less than mV of the positive supply rail value. The sensitivity of the Figure 1 and 2 circuits can be increased by replacing Q1 with a pair of Darlington- or Super-Alpha-connected transistors.

The Figure 3 circuit uses two npn transistors. When the input is at zero volts, Q1 is cut off, so Q2 is driven fully on via R2, and the output is low saturated. The Figure 4 circuit uses one npn and one pnp transistor.

When the input is at zero volts, Q1 is cut off, so Q2 is also cut off via R2-R3 and the output is at zero volts. Under this condition, the output takes up a value a few hundred mV below the positive supply rail value. Figure 5 shows in basic form how a complementary pair of the Figure 4 circuits can be used to make a DC-motor direction-control network, using a dual power supply.

The circuit operates as follows. The basic digital circuits of Figures 1 through 4 can be used as efficient relay drivers if fitted with suitable diode protection networks.

Figures 6 through 8 show examples of such circuits. R1 gives base drive protection, and can be larger than 1k0, if desired. The relay is turned on by a positive input voltage. The current sensitivity of the relay can be raised by a factor of about 20, by replacing Q1 with a Darlington-connected pair of transistors.

Figure 7 shows this technique used to make a circuit that can be activated by placing a resistance of less than 2M0 across a pair of stainless metal probes. Water, steam, and skin contacts have resistances below this value, so this simple little circuit can be used as a water, steam, or touch-activated relay switch.

Touch, water, or steam-activated relay switch. R2 ensures that Q1 and Q2 turn completely off when the input terminals are open circuit. A common-emitter circuit can be used as a linear AC amplifier by applying a DC bias current to its base so that its collector takes up a quiescent half-supply voltage value to accommodate maximal undistorted output signal swings , and by then feeding the AC input signal to its base and taking the AC output from its collector as shown in Figure 9.

The first step in designing a circuit of the basic Figure 9 type is to select the value of load resistor R2. In the example shown, the input impedance is roughly 5k0, and is shunted by R1 — the voltage gain works out at about x, or 46dB. The feedback action is such that any shift in the output level due to variations in h fe , temperature, or component values causes a counter-change in the base-current biasing level, thus tending to cancel the original shift.

Common-emitter amplifier with feedback biasing. The Figure 10 circuit has the same values of bandwidth and voltage gain as the Figure 9 design, but has a lower total value of input impedance. If desired, the shunting effects of the biasing network can be eliminated by using two feedback resistors and AC-decoupling them as shown in Figure Amplifier with AC-decoupled feedback biasing.

Figures 13 to 16 show some useful common-emitter amplifier variations. Alternative gain values can be obtained by altering the R5 value. Fixed-gain x10 common-emitter amplifier. Figure 14 shows a useful variation of the above design. In this case, R3 equals R4, and is not decoupled, so the circuit gives unity voltage gain. Note, however, that this circuit gives two unity-gain output signals, with the emitter output in phase with the input and the collector signal in anti-phase.

This circuit thus acts as a unity-gain phase splitter. Figure 15 shows another way of varying circuit gain. Finally, Figure 16 shows how the Figure 10 design can be modified to give a wide-band performance by wiring DC-coupled emitter follower buffer Q2 between Q1 collector and the output terminal, to minimize the shunting effects of stray capacitance on R2, and thus extending the upper bandwidth to several hundred kHz. A single-stage common-emitter amplifier circuit cannot give a voltage gain much greater that 46dB when using a resistive collector load — a multi-stage circuit must be used if higher gain is needed.

Figures 17 to 19 show three useful high-gain, two-transistor voltage amplifier designs. Figure 18 shows an alternative version of the above design, using a pnp output stage — its performance is the same as that of Figure Alternative high-gain two-stage amplifier. The Figure 19 circuit gives a voltage gain of about 66dB.

Q1 thus gives a very high voltage gain. The common-base amplifier has a very low input impedance, gives near-unity current gain and a high voltage gain, and is used mainly in wide-band or high-frequency voltage amplifier applications.

Figure 20 shows an example of a common-base amplifier that gives a good wide-band response. The Figure 20 circuit is biased in the same way as Figure Note, however, that the base is AC-decoupled via C1, and the input signal is applied to the emitter via C3.

This is achieved by wiring Q1 and Q2 in series, with Q1 connected in the common-base mode and Q2 in the common-emitter mode. The input signal is applied to the base of Q2, which uses Q1 emitter as its collector load and thus gives unity voltage gain and a very wide bandwidth, and Q1 gives a voltage gain of about 46dB.

Thus, the complete circuit has an input impedance of about 1k8, a voltage gain of 46dB, and a -3dB bandwidth that extends to a few MHz. The circuit acts as follows. Suppose that a sinewave input signal is fed to Q2 base. Q2 acts as an inverting common-emitter amplifier, and when the signal drives its base upward, its collector inevitably swings downward, and vice versa. Q1 thus operates in the common-base mode and gives the same voltage gain as Q2, but gives a non-inverting amplifier action.

Finally, Figure 23 shows how the above circuit can be made to act as a differential amplifier that gives a pair of anti-phase outputs that are proportional to the difference between the two input signals — if identical signals are applied to both inputs, the circuit will ideally give zero output. Simple differential amplifier or long-tailed pair. This eight-part series focuses on basic transistor theory, characteristics, and presents a wide range of practical bipolar transistor application circuits.

Need to brush up on your electronics principles? These multi-part series may be just what you need! Everything for Electronics. Forum Blogs Feedback Techforum Newsletter.

All articles in this series: Bipolar transistor principles and basic circuit configurations. Part 1 of 8 A variety of practical common-collector amplifier circuits. Part 2 of 8 Practical common-emitter and common-base amplifier circuits. Part 3 of 8 A variety of practical small-signal audio amplifier circuits in this edition.

Part 4 of 8 Practical oscillator and white noise waveform generator circuits. Part 5 of 8 Practical multivibrator types of waveform generator circuits. Part 6 of 8 Practical transistor audio power amplifier and 'accessory' circuits. Part 7 of 8 A miscellaneous collection of useful transistor circuits and gadgets in this final episode.

Part 8 of 8. Popular Stories Wirespondence! Turing Machines s Radio Applause Cards. Learning Electronics Need to brush up on your electronics principles?

Simple two transistor amplifier

Most of the electronic systems require at least one stage of amplification. Hence amplifiers can be seen in almost all the electronic devices. Amplifiers are the devices that increase the amplitude of the input signal. The output of the power supply is modulated by the Amplifier. Amplifiers increase only the amplitude and the other parameters such as frequency and shape remain constant. There are many types of amplifiers available. But they can be distinguished by the type of signal they amplify.

Capacitor Selection for Coupling and Decoupling Applications

The common-emitter amplifier also known as the common-earth or grounded-emitter circuit has a medium value of input impedance and provides substantial voltage gain between input and output. The common-emitter amplifier can be used in a wide variety of digital and analog voltage amplifier applications. When the input is zero, the transistor is cut off and the output is at full positive supply rail value. When the input is high, the transistor is biased on and a collector current flows via R L , thus pulling the output low. Thus, the output signal is an amplified and inverted version of the input signal. In Figure 1 , resistor R b limits the input base-drive current to a safe value. In practice, R b should be as small as possible, consistent with safety and input-impedance requirements, and must not exceed R L x h fe.

Video Amplifiers

Skip to Main Content. A not-for-profit organization, IEEE is the world's largest technical professional organization dedicated to advancing technology for the benefit of humanity. Use of this web site signifies your agreement to the terms and conditions. Common-Emitter Transistor Video Amplifiers Abstract: A design procedure and theory are given for the common-emitter transistor video amplifier with and without a feedback resistor in the emitter lead. In the analysis a junction transistor of the alloy type is represented by the Johnson-Giacoletto hybrid-pi equivalent circuit for the common-emitter transistor.

Simple Video Amplifier

This is a video amplifier splitter circuit or the video splitter circuit. It is designed to take video signal is stronger and compensate for the loss of signal. Also, it is a video splitter up to three outputs. So, it is suitable for display on several television screens, or videotapes recording at the same time, too. Now, may no a videotape.

US2921196A - Transistor regenerative detector circuit - Google Patents

An amplifier , electronic amplifier or informally amp is an electronic device that can increase the power of a signal a time-varying voltage or current. It is a two-port electronic circuit that uses electric power from a power supply to increase the amplitude of a signal applied to its input terminals, producing a proportionally greater amplitude signal at its output. The amount of amplification provided by an amplifier is measured by its gain : the ratio of output voltage, current, or power to input. An amplifier is a circuit that has a power gain greater than one. An amplifier can either be a separate piece of equipment or an electrical circuit contained within another device.

transistor amplifier Circuit Using BC547 Transistors

You can now explain with confidence what p-doping, n-doping, and depletion layers mean. Now you will put that knowledge to use. You have the transistor in your hand.

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RELATED VIDEO: How to make 100W amplifier circuit using two transistors 2N3055

In practical applications, the output of a single state amplifier is usually insufficient, though it is a voltage or power amplifier. Hence they are replaced by Multi-stage transistor amplifiers. In Multi-stage amplifiers, the output of first stage is coupled to the input of next stage using a coupling device. These coupling devices can usually be a capacitor or a transformer.

Multi-Stage Transistor Amplifier

Diy Transistor Amp. So we consider 3. Therefore, in this case, a voltage amplifier is built with all simple, discrete components. The diyAudio store will continue to receive your chassis orders. There are a seemingly infinite variety of transistor amplifiers out there, but fortunately a lot of them are based on some of these more primitive circuits. Sometimes we use the pre-amplifier circuit to amplify the weak signals for detection So in this tutorial, we will build a Simple Preamplifier Circuit using NPN transistor BC Also to increase a small audio signal to strength to go into a power amplifier circuit.

Different Types and Applications of Amplifiers

The present invention relates to a complementary transistor circuit and, an amplifier using it, and in particular, to a video amplifier for amplifying video signals and a high-definition CRT display device. In amplifying inputted video signals by using a multiplexer, a gain controller and a current mirror amplifier, each element circuit is formed by using complementary transistor circuits. Circuit simplification is thus attained.