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Output transformer transistor amplifier schematic

An audio amplifier with a transistorized power output stage furnishes an amplified audio signal to an autotransformer. The autotransformer has a plurality of taps to permit the selection of any of a plurality of output impedance levels. The autotransformer is wound on a bobbin in a novel manner so as to minimize distortion of the audio signal. Audio amplifiers are commonly designed to accommodate any of several different loads having different impedances. Typically, an audio amplifier will be provided with output terminals for driving speaker systems having 2, 4 or 8 ohm impedances. In order to provide impedance matching between the amplifier circuit and the loud speaker system, conventional audio amplifier circuits employ output transformers which have a primary winding driven by the power output stage of the amplifier and an electrically separate secondary winding having a plurality of taps to provide plural outputs at different impedance levels.


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WATCH RELATED VIDEO: 1000watt output transformer winding data - 1000 watt amplifier output transformer

2N3773 2SC5200 Amplifier Circuit 150W


In multi-stage amplifiers, coupling devices are used to connect different stages of transistor circuits in cascade. The coupling devices would be a transformer or resistor or capacitor.

To overcome the drawbacks of RC coupled amplifiers like high impedance at the output, low impedance at the input, reduced resistance at the load, and reduced voltage gain, a transformer-coupled amplifier is introduced. Here is a brief note in the Transformer-coupled amplifier. In multi-stage amplifier circuits, when the output of the first stage is connected to the input of the second stage in cascade through the transformer, then it is called a Transformer Coupled Amplifier.

Here Transformer acts as a coupled amplifier. It has a high impedance at the input, a low impedance at the output, a higher voltage gain, higher efficiency, and increased effective load resistance. It is applicable when the load is low and mainly used for power amplification.

The turn ratio of a transformer can be utilized for matching impedance with the load. This type of coupling can be used in high-frequency amplifier circuits in the range of Radio Frequency and Intermediate frequency. When the output of one stage is connected to the input of another stage through a coupled transformer, then it is called a transformer-coupled amplifier. The circuit diagram of the transformer-coupled amplifier is shown below. The coupling transformer T1 is connected between the output of the first stage and the input of the second stage.

The collector of the transistor in the first stage is connected to the primary winding of T1 while the secondary winding of T1 is between potential divider R1 and the transistor base in the second stage.

Instead of resistor and capacitor, a transformer is used in a transformer-coupled amplifier circuit to achieve high voltage gain and efficiency. Similarly, multiple stages can be formed by the coupling of the transformer.

R1, R2, and resistor Re are the potential dividers used for biasing and stabilization purposes. The low reactance path is provided by the by-pass capacitor Ce at the emitter junction of the second stage to the output signal of the first stage. Whereas the coupling capacitor Cc is used to connect these two stages by isolating DC interference from one stage to another stage and also controls the operation.

The input capacitor Cin in the first stage allows the AC signal to the base of the transistor. When Resistor-capacitor is used as a coupling device, the effective load resistance could decrease due to the high output impedance of the first stage would come in parallel with the low input impedance of the second stage.

So, a transformer is used to overcome this problem in the coupling of multi-stage amplifiers. The AC input signal applied in the first stage flows through the input capacitor to the base of the transistor by eliminating DC components in the signal.

This input signal gets amplified by the transistor in the first stage and it is collected by the primary winding of the transformer T1. Here T1 transformer is used for coupling two stages. The signal, which is amplified in the first stage is fed to the input of the second stage through the secondary winding of T1. Due to the matching property of coupled transformer T1 like matching of impedance property, the low resistance of the load of one stage can be reflected as high load resistance to the previous stage.

The voltage of the amplified signal at the primary winding can be converted in accordance with the turns ratio of the secondary winding of T1. This method provides better impedance matching properties, used for power amplification. The output of the circuit has low DC resistance, higher efficiency, higher voltage gain, high input impedance, and low output impedance.

The output of the coupling transformer can be referred to as the final output because of its impedance matching properties. Note: The primary winding of T1 acts as a load on the first stage of the transistor while the secondary winding of T1 is for impedance matching for the next stage transistor.

The capacitors resonance and increases the selectivity for a range of frequencies that is to be amplified. The frequency response of the transformer-coupled amplifier is shown below. The frequency response is drawn between voltage gain in dB and frequency in Hz. For a small range of frequencies, the gain of the amplifier is constant.

We can get the output voltage, which is equal to the multiplication of the collector current and the reactance of the primary winding of coupling transformer T1. The frequency response characteristics are drawn between the voltage gain dB and input frequency. In the lower-frequency range, the reactance of primary winding starts reducing, which results in a decreased gain.

Whereas at higher frequencies, the bypass condenser capacitance between the turns of two windings reduces the voltage at the output and gain. So, the signal cannot be amplified and some distortion is occurred, called frequency distortion.

Please refer to this link to know more about Transformer Question and Answers. Thus, this is all about the transformer-coupled amplifier — definition , circuit diagram, working, advantages, disadvantages, and applications. Transformer Coupled Amplifier. Frequency Response of Amplifier.


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We have observed that the main drawback of RC coupled amplifier is that the effective load resistance gets reduced. This is because, the input impedance of an amplifier is low, while its output impedance is high. When they are coupled to make a multistage amplifier, the high output impedance of one stage comes in parallel with the low input impedance of next stage. Hence, effective load resistance is decreased. This problem can be overcome by a transformer coupled amplifier. In a transformer-coupled amplifier, the stages of amplifier are coupled using a transformer.

When they are coupled to make a multistage amplifier, the high output impedance of one stage comes in parallel with the low input impedance of next stage. Hence.

US3025412A - Transistor amplifier circuits - Google Patents


This circuit shows a complete class AB output stage and driver stage. The driver stage works in the same manner as the class A output stage described previously. However it is only working at a couple of milliamps, so efficiency is not an issue here. The biasing arrangement should be familiar by now. Some sets, including the circuit above, have an extra stage of amplification between the volume control and the driver stage. Such sets will be able to receive weaker stations better and probably produce higher volume or better quality on stronger signals. This would take the total to seven transistors, whereas sets without this stage have six transistors. The extra amplification stage VT1 and related components works as described in the basic common-emitter amplifier section earlier. In this design, negative feedback is coupled round from the output, back to the input of the driver stage via R8, to reduce distortion and improve quality.

US3952256A - Multi-impedance output for transistor power amplifier - Google Patents

output transformer transistor amplifier schematic

The design of audio transformers is different in many respects from the design of power transformers. The principal reason for this difference is that audio transformers must maintain a constant ratio of input to output voltage over a band of frequencies, rather than a single frequency. The problems inherent in this requirement become more severe as the width of the passband increases. The passband is the band over which the input to output voltage remains within prescribed limits of deviation from some arbitrary reference frequency.

This is a 4 transistor audio amplifier circuit. Which is a 4-transistors complementary push-pull amplifier, that shows the basics of audio amplifier design.

Transformer Coupled Amplifier


In this article we are discussing a handful of mini audio amplifier circuit which can be built quickly for amplifying very tiny input signals into audible speaker outputs. The first mini audio amplifier circuit works with a 'complementary' output stage, having a single NPN and a single PNP power transistor, that gets rid of an output transformer commonly observed in older amplifier models. Power output is around 1W, with fairly minimal distortion. The input signal is transferred via the volume control RV1 and next through C1 to the Q1 base. The collector load for Q1 consists of R1, R5 along with the loudspeaker.

Audio Transformers

Modern operational amplifiers op amps and instrumentation amplifiers in-amps provide great benefits to the designer, compared with assemblies of discrete semiconductors. A great many clever, useful, and tempting circuit applications have been published. This article will discuss a few of the most common application problems and suggest practical solutions. One of the most common application problems encountered is the failure to provide a dc return path for bias current in ac-coupled operational- or instrumentation-amplifier circuits. Depending on the polarity of the input bias current, the capacitor will charge up toward the positive supply voltage or down toward the negative supply. The bias voltage is amplified by the closed-loop dc gain of the amplifier. This process can take a long time. For example, an amplifier with a field-effect-transistor FET input, having a 1-pA bias current, coupled via a 0.

Class A power amplifier with resistive and transformer coupled load - calculation the output circuit and converts it into a.c. signal power.

4 transistor audio amplifier circuit

Return to Homebrew Radios and Equipment. Transistor Amplifier with output transformer Ads are not permitted. Transistor Amplifier with output transformer by Macrohenry » Aug Thu 16, am I'm trying to understand why different transistor amplifier circuits perform so differently. In my studies, much attention is paid to matching impedances for optimum operation.

What is Transformer Coupled Amplifier & Its Working


March 13, J. Feiker, Livingston, NJ. One such pulse amplifier is described in my Patent 2,,- , February 23, , 'wherein feedback is attained through the base circuit of the transistor. In application Serial No.

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Push–pull output

A push—pull amplifier is a type of electronic circuit that uses a pair of active devices that alternately supply current to, or absorb current from, a connected load. This kind of amplifier can enhance both the load capacity and switching speed. Push—pull outputs are present in TTL and CMOS digital logic circuits and in some types of amplifiers , and are usually realized by a complementary pair of transistors , one dissipating or sinking current from the load to ground or a negative power supply, and the other supplying or sourcing current to the load from a positive power supply. A push—pull amplifier is more efficient than a single-ended "class-A" amplifier. The output power that can be achieved is higher than the continuous dissipation rating of either transistor or tube used alone and increases the power available for a given supply voltage. Symmetrical construction of the two sides of the amplifier means that even-order harmonics are cancelled, which can reduce distortion. However, the push—pull amplifier requires a phase-splitting component that adds complexity and cost to the system; use of center-tapped transformers for input and output is a common technique but adds weight and restricts performance.

One of the most popular applications of transistors is in audio power amplifiers. This month we describe the operating principles of various circuits of this type and present a selection of practical audio power amplifier circuit designs. A transistor power amplifier's job is that of converting a medium-level medium-impedance AC input signal into a high-level low-impedance state suitable for driving a low-impedance external load.




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