Darlington differential amplifier design

Emitter follower and darlington amplifier are the most common examples for feedback amplifiers. These are the mostly used ones with a number of applications. Emitter follower circuit has a prominent place in feedback amplifiers. Emitter follower is a case of negative current feedback circuit. This is mostly used as a last stage amplifier in signal generator circuits. All these ideal features allow many applications for the emitter follower circuit.

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Content:

• Darlington transistor
• A darlington pair transistor based operational amplifier
• Darlington Transistor (Darlington Pair)
• Emitter Follower & Darlington Amplifier
• Theory and Applications of Darlington Pair Amplifier
• Darlington bootstrap amplifier pdf
• Know all about Darlington Transistor Pair
• A Darlington Pair Based CMOS Two Stage Operational Amplifier at 32nm Technology
• US20050104659A1 - Darlington differential amplifier - Google Patents

WATCH RELATED VIDEO: Darlington Pair

Darlington transistor

Effective date : Year of fee payment : 4. Year of fee payment : 8. Year of fee payment : 7. Year of fee payment : A Darlington differential amplifier includes a differential pair of Darlington transistors, with each pair including a first transistor and a second transistor connected in cascade to the first transistor. The first transistor is controlled by an externally generated voltage and drives the second transistor. The first and second transistors each include first and second conducting terminals, with the first conducting terminals being connected together and forming an output node of the amplifier.

A first degeneration impedance is connected between the second conduction terminals of the second transistors in the pair of Darlington transistors. A second degeneration impedance is connected between the second conduction terminals of the first transistors in the pair of Darlington transistors for reducing harmonic distortion of the amplifier.

In many applications it is desirable to have high gain amplifiers, and at the same time have a linear transfer characteristic to prevent distortions of the signal to be amplified.

An architecture of a differential amplifier commonly used in communication systems, in which these requirements are particularly desired, is a Darlington differential amplifier as shown in FIG.

The illustrated Darlington differential amplifier is formed with bipolar transistors. The Darlington transistors are coupled between them through two identical emitter degeneration resistors RE 1 , RE 2. These amplifiers are characterized by high gains approximately equal to the ratio between the load resistance RC 1 or RC 2 and the emitter degeneration resistances RE 1 or RE 2.

The resistors RC 1 and RC 2 are generally determined by external circuits connected to the amplifier, such as via a cable or an antenna. The resistors RC 1 and RC 2 cannot be modified. As a consequence, it is necessary to reduce the resistances RE 1 and RE 2 to increment the gain.

To summarize, the transfer characteristic of the amplifier is even more linear as the product between the collector current IC 1 or IC 2 and the resistance RE 1 or RE 2 increases. When values of the emitter resistance are chosen too small, this increases the current IC 1 or IC 2 for a sufficiently linear transfer characteristic.

Consequently, the power dissipated by the amplifier is increased. An object of the invention is to provide a Darlington differential amplifier characterized by high gains and a reduced distortion of the amplified signal. The third order harmonic distortion of the amplifier may be reduced without modifying substantially its gain by connecting a degeneration impedance between the Darlington transistors.

The type and value of this impedance are design variables that are properly chosen for reducing the harmonic distortion at a given operating frequency. More precisely, the invention provides a Darlington differential amplifier comprising a differential pair of Darlington transistors each composed of a first transistor controlled by an externally generated voltage and driving a second transistor in cascade.

Degeneration impedances are connected between the emitter or source nodes of the second transistors. The amplifier of the invention shows a more linear transfer characteristic with the same gain with respect to the known amplifiers because it comprises a second degeneration impedance for reducing the harmonic distortion of the differential amplifier. The second degeneration impedance is connected between the emitter or source nodes of the first transistors of the differential pair of Darlington transistors.

Preferably, the second degeneration impedance is composed of two identical resistive impedances electrically in series, and a current generator is connected between their common node and a ground node.

The different aspects and advantages of the invention will be even more evident through a detailed description referring to the attached drawings, wherein:.

An embodiment of a Darlington differential amplifier of the invention is depicted in FIG. Differently from the known amplifier of FIG. A current generator ID is connected between the common node to the two degeneration resistors and a ground node. In the shown example, bipolar transistors are used, but the same considerations also hold if the bipolar transistors are replaced with MOSFETs. The harmonic distortion of the amplifier of the invention, that is the ratio in decibel between the amplitude of the third harmonic component and the amplitude of the fundamental harmonic of the output signal at a test frequency, may be reduced by appropriately choosing the degeneration resistances.

This leaves practically unchanged the gain of the amplifier. The diagram of FIG. This graph has been obtained by simulating the circuit of FIG. As it is possible to infer from FIG. As a matter of fact, near the minimum an almost perfect cancellation of the third order harmonic takes place, but this is not highlighted in the graph because of the limited number of points considered for the simulation.

The gain of the amplifier is substantially unchanged, because it is essentially determined by the emitter degeneration resistances RE 1 , RE 2 and by the load resistances RC 1 , RC 2. The additional current generator ID is not indispensable, but it has been noticed that it contributes in reducing the harmonic distortion by choosing for it an optimal value determined by trial and error for each case. Each current generator is connected between the ground node and a respective emitter source node of the transistors QD 1 and QD 2.

According to alternative embodiments of the invention, the degeneration impedances connected between the emitters of the transistors Q 1 , Q 2 and QD 1 and QD 2 may be as depicted in FIGS. The impedances Z are resistive or inductive and are determined to reduce the third order harmonic distortion of the output signal at frequencies at which the amplifier shall operate.

A Darlington differential amplifier comprising: a differential pair of Darlington transistors, each pair comprising a first transistor and a second transistor connected in cascade to said first transistor, said first transistor being controlled by an externally generated voltage and driving said second transistor, said first and second transistors each comprising first and second conducting terminals, the first conducting terminals being connected together and forming an output node of the amplifier;.

A Darlington differential amplifier according to claim 7 , wherein said first degeneration impedance comprises a pair of identical resistors or inductors connected together in series.

A Darlington differential amplifier according to claim 8 , further comprising a capacitor connected in parallel to said pair of resistors or inductors. A Darlington differential amplifier according to claim 9 , further comprising a resistor or inductor connected in series with said capacitor and also connected in parallel to said pair of resistors or inductors. A Darlington differential amplifier according to claim 7 , wherein said second degeneration impedance comprises a pair of resistors or inductors connected together in series.

A Darlington differential amplifier according to claim 11 , further comprising a capacitor connected in parallel to said pair of resistors or inductors. A Darlington differential amplifier according to claim 12 , further comprising a resistor or inductor connected in series with said capacitor and also connected in parallel to said pair of resistors or inductors.

A Darlington differential amplifier according to claim 11 , wherein said pair of resistors or inductors are connected together at a common node; and further comprising a current generator connected between the common node and ground. A Darlington differential amplifier according to claim 11 , further comprising a pair of current generators connected between ground and a respective second conducting terminal of said first transistors in said pair of Darlington transistors.

A differential amplifier comprising: first and second pairs of transistors connected together, each pair of transistors comprising a first transistor and a second transistor connected in cascade to said first transistor, said first transistor driving said second transistor, said first and second transistors each comprising first and second conducting terminals, the first conducting terminals being connected together and forming an output node of the amplifier;.

A differential amplifier according to claim 16 , wherein said first degeneration impedance comprises a pair of identical resistors or inductors connected together in series. A differential amplifier according to claim 17 , further comprising a capacitor connected in parallel to said pair of resistors or inductors. A differential amplifier according to claim 18 , further comprising a resistor or inductor connected in series with said capacitor and connected in parallel to said pair of resistors or inductors.

A differential amplifier according to claim 16 , wherein said second degeneration impedance comprises a pair of resistors or inductors connected together in series.

A differential amplifier according to claim 20 , further comprising a capacitor connected in parallel to said pair of resistors or inductors.

A differential amplifier according to claim 21 , further comprising a resistor or inductor connected in series with said capacitor and connected in parallel to said pair of resistors or inductors. A differential amplifier according to claim 20 , wherein said pair of pair of resistors or inductors are connected together at a common node; and further comprising a current generator connected between the common node and ground.

A differential amplifier according to claim 20 , further comprising a pair of current generators connected to between ground and a respective second conducting terminal of said first transistors. A method for making a Darlington differential amplifier comprising: forming a differential pair of Darlington transistors, each pair comprising a first transistor and a second transistor connected in cascade to the first transistor, the first transistor being controlled by an externally generated voltage and driving the second transistor, the first and second transistors each comprising first and second conducting terminals, the first conducting terminals being connected together and forming an output node of the amplifier;.

A method according to claim 25 , wherein the first degeneration impedance comprises a pair of identical resistors or inductors connected together in series.

A method according to claim 26 , further comprising connecting a capacitor in parallel to the pair of resistors or inductors. A method according to claim 27 , further comprising connecting a resistor or inductor in series with the capacitor and also in parallel to the pair of resistors or inductors.

A method according to claim 25 , wherein the second degeneration impedance comprises a pair of resistors or inductors connected together in series. A method according to claim 29 , further comprising connecting a capacitor in parallel to the pair of resistors or inductors.

A method according to claim 30 , further comprising connecting a resistor or inductor in series with the capacitor and also in parallel to the pair of resistors or inductors. A method according to claim 29 , wherein the pair of resistors or inductors are connected together at a common node; and further comprising connecting a current generator between the common node and ground. A method according to claim 29 , further comprising connecting a pair of current generators between ground and a respective second conducting terminal of the first transistors in the pair of Darlington transistors.

USB2 en. ITVAA1 en. JPB2 en. Minaei et al. A new CMOS electronically tunable current conveyor and its application to current-mode filters. EPB1 en. Differential amplifier with current source controlled through differential feedback. USB1 en. EPA2 en. USA en.

USA1 en. WOA1 en. JPA en. DKB en. Comer et al. JPHA en. CNA en.

A darlington pair transistor based operational amplifier

Verified Supplier. Get Latest Price. The cascode amplifier configuration consists of a common emitter stage followed by a common base stage. The two major advantages of a cascode amplifier are a low load resistance which results in an improved frequency response and a high output frequency response and a high output resistance.

Darlington Transistor (Darlington Pair)

Effective date : Year of fee payment : 4. Year of fee payment : 8. Year of fee payment : 7. Year of fee payment : A Darlington differential amplifier includes a differential pair of Darlington transistors, with each pair including a first transistor and a second transistor connected in cascade to the first transistor. The first transistor is controlled by an externally generated voltage and drives the second transistor. The first and second transistors each include first and second conducting terminals, with the first conducting terminals being connected together and forming an output node of the amplifier.

Emitter Follower & Darlington Amplifier

In electronics , a multi-transistor configuration called the Darlington configuration commonly called a Darlington pair is a circuit consisting of two bipolar transistors with the emitter of one transistor connected to the base of the other, such that the current amplified by the first transistor is amplified further by the second one. This configuration has a much higher current gain than each transistor taken separately. It acts like and is often packaged as a single transistor. It was invented in by Sidney Darlington. A Darlington pair behaves like a single transistor, meaning it has one base, collector, and emitter.

Theory and Applications of Darlington Pair Amplifier

In electrical and electronic circuits, Darlington transistor or Darlington transistor pair is an essential component. It consists of two bipolar transistors, that are connected in such a way that the current amplifies by the first transistor then by the second transistor. The configuration of the Darlington transistor gives a much higher current gain than a single transistor taken individually. For more details regarding Darlington transistor follow the below link. Darlington transistor working along with its applications.

Darlington bootstrap amplifier pdf

Interfaces and Transceivers Minimize menu. Please log in to show your saved searches. Darlington devices are high-voltage, high-current switch arrays containing multiple open-collector Darlington pairs or multiple Darlington transistors with common emitters, and integral suppression diodes for inductive loads. The nominal current rating of each output is mA for the 7- and 8-output devices and up to 1. The inputs are pinned opposite the outputs to simplify the application board layout. These devices interface standard logic families. This browser is out of date and not supported by st.

Know all about Darlington Transistor Pair

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A Darlington Pair Based CMOS Two Stage Operational Amplifier at 32nm Technology

RELATED VIDEO: Darlington Amplifier

Start Learning English Hindi. This question was previously asked in. High input impedance, high output impedance, and high current gain Low input impedance, low output impedance, and low voltage gain High input impedance, low output impedance, and high current gain Low input impedance, low output impedance, and high current gain. Answer Detailed Solution Below Option 3 : High input impedance, low output impedance, and high current gain.

US20050104659A1 - Darlington differential amplifier - Google Patents

The Differential Amplifier Circuit using Transistors is widely applied in integrated circuitry, because it has both good bias stability and good voltage gain without the use of large bypass capacitors. Differential amplifiers can also be constructed as discrete component circuits. Figure a shows that a basic Differential Amplifier Circuit using Transistors consists of two voltage divider bias circuits with a single emitter resistor. Like the emitter current in a single-transistor voltage divider bias circuit, I E in the differential amplifier remains virtually constant regardless of the transistor h FE value. So, the differential amplifier has the same excellent bias stability as a single-transistor voltage divider bias circuit. The circuit of a Differential Amplifier Circuit using Transistors using a plus-minus supply is shown in Fig.

So output current flows for complete cycle of input signal. Here, we have used bootstrapping technique to increase the input impedance of this amplifier circuit. Effect of bias resistance can be minimised by bootstrapping the cc circuit as shown. These are the mostly used ones with a number of applications.