Skip to content

Understanding the Amplifier Circuit Diagram

Electronic or electrical amplifiers can be described as circuits which make use of external power supply or generating output signals which are a bigger replica of the input.

Audio amplifiers, which can be described as a recognizable application, are useful for increasing a speaker’s volume to allow the sound to be heard easily in any large area. Though voltage can be described as the most common of all amplified input signals, these amplifiers may also be designed so as to increase the current. Any amplifier which increases the current drive of an output is referred to as the power amplifier.

Majority of amplifiers perform linear amplification. However, some are naturally logarithmic. In circuit diagrams, amplifiers are represented with a triangle. First, let us consider what an amplifier circuit diagram means as well as its types.

What Does Amplifier Circuit Diagrams Mean?

Amplifier PCB

Amplifier circuit diagrams are made up of one signal pick-up transducer, which is followed by any small signal amplifier, output transducer, as well as one large signal amplifier. Initially, the amplifier circuit diagram comes in two types i.e. power amplifier circuits and voltage amplifier circuits.

Voltage amplifier circuit

The main function of this type of amplifier circuit diagram is to help in raising the signal’s voltage level. It is specially designed for achieving the largest gain possible. You can draw extremely little power out of the output. In order to achieve any high amplification of voltage, then the requirements below has to be met by your voltage amplifier circuits.

  • The transducer features a thin base i.e. beta/high transistors (higher than 100) is utilized.
  • Fairly low impedance compared to the output impedance.
  • The voltage amplifier will always function at a low current of around 1mA, in order to allow high collector loads that are required for a high gain in voltage.
  • Most of the time, the R-C couple is necessary for coupling the different voltage amplifier circuit stages due to the fact that it is cheaper when it comes to portability and cost.

Power amplifier circuit

The main function of this type of amplifier circuit diagram is to raise the input signal’s power level. In order to get a large power for the output, then there must be a large input-signal voltage. This is why for electronic systems, voltage amplifier circuits usually precedes the power amplifier circuits. Also, this is the reason behind power amplifier circuits called the large-signal amplifier circuits.

The regions found behind power amplifier circuits is referred to as large-signal amplifier circuits because it has the ability to draw power out of the DC source, which is connected in the output and then converts it in an appropriate AC signal or sine wave. Power amplification cannot occur here because it doesn’t work in line with the physics’ rule. In order to achieve greater power amplification, then the circuit has to work with the requirements below

  • For power amplification, there is heat produced in a transistor during an operation, to ensure large-sized power transistors are used
  • Collector resistance is made low
  • Transistors with thick bases not voltage amplifier (beta/smaller) is useful in handling large currents
  • Most times the transformer-couple is useful in impedance matching.

What are the Important Features of Amplifier Circuits?

An amplifier’s quality may be measured through some specifications referred to as the figures of merit. Let’s consider them

  • Noise: This refers to the additional information that is unwanted, but included inside the output
  • Bandwidth: This is the range of frequency where the amplifier will be able to function
  • Skew rate: This is highest rate of output change
  • Linearity: degree of proportionality found in-between the output and input signals
  • Gain: This is the most significant. It is the ratio between the output and input signals magnitudes
  • Stability: Ability to provide reliable and constant output.
  • Output dynamic range: This describes the ratio between the smallest and largest useful levels of output

What Amplifier Types are There?

Aside from the main or basic types, amplifiers come in several types. This is grouped by their characteristics, application or operation. Some of them include

Power Amplifiers

Though not a type from the technical point of view, the power amplifiers form a general term which has to do with the quantity of power provided by your power supply circuits as well as the power that is delivered onto the load. This is usually utilized in a circuit’s final output stages.

Some examples are push-pull amplifiers, servo motor amplifiers, audio power amplifiers, as well as the RF power amplifier.  Once again, we will be considering how power amplifiers are classified, because they play a very significant role.

Operational Amplifiers

This is another important type, also known as op-amps. This is an IC which functions as voltage amplifiers. It also has a differential input. Furthermore, it features a negative and positive input, as well as one output with extremely high gain. Initially, the creation of op-amps was done using valves.

Transistor Amplifiers

This is a popular type of amplifier that is especially designed for engineering students. It is a well-known amplifier. It is a high output multi-configuration amplifier which makes use of transistors as its working base.

Vacuum (or) Valve tube amplifiers

This type of amplifier makes use of vacuum tubes for providing increased voltage or power output. As mentioned earlier, op-amps were initially the valve type; however, the ICs replaced them as soon as they became less expensive, at least, in the smaller applications. However, for high-power applications, they are still useful due to their output quality and cost effectiveness. Also, they are useful in military, radar, high power UHF and radio transmitter applications.


This is a special linear vacuum tube utilized as amplifiers in the high-radio frequencies. Also, it is very precise and is useful in large-scale operations, and usually categorized microwave amplifiers.

Distributed Amplifiers

These are amplifiers, which makes use of transmission lines for splitting the input temporarily as well as amplifying each segment. You can find them in oscilloscopes.

Instrument Amplifiers

These amplifiers are specially designed for amplifying music, voice, or sound. It is mainly used in applications for musical instruments.

Different Circuit Currents

Let’s consider the different circuit currents present in a full amplifier circuit board diagram.

Base Current

Whenever there is no applied signal on a base circuit, the DC base current will flow as a result of the biasing current. Whenever the AC signal has been removed, the AC base current will also flow.

Emitter current

The DC emitter current will flow whenever there is no signal applied.

Collector current

Whenever there is no signal applied, the DC collector IC will flow because of the biasing current. Whenever an AC signal has been applied, then the AC collector current flows as well.

Practical Circuit of the Transistor Amplifier

Antenna Amplifier PCBA BOARD

The practical circuit of the transistor amplifier represents a specific voltage divider biasing circuit. The different prominent elements of a circuit as well as their function can be described below.

Input Capacitor

The capacitor helps in the coupling of an input signal to the transistor’s base. Input capacitor permits an AC signal, but helps in isolating a source of signal. When the capacitor isn’t present, then the input signal will become applied directly, thereby changing the bias.

Biasing Circuit

Resistors RE, R2, and R1 form the stabilization and biasing circuit. This aids in establishing the right point of operation.

Emitter by-pass capacitors

You can employ the capacitor in the parallel form into your emitter resistor. Thee

Coupling Capacitor

This capacitor is usually seen at the final periods of one stage and then connects it onto the second stage. Because it helps in the coupling of two stages, you can call it a coupling capacitor. The capacitor will block the DC of one of the stages and make it enter the second but permits the passing of the AC. This is why it is referred to as the blocking capacitor.

Because of the coupling capacitor, the output that forms across the resistor is completely free from the DC voltage of the collector. When you don’t find this, the next phase’ bias conditions would be changed drastically as a result of the RC’s shunting effect because it would come in a parallel form to the following stage.

Load Resistor

The resistance that is connected at its output is referred to as the load resistor. Whenever a number of phases are utilized, then the RL represents the next stage’s input resistance.


By now, you should understand what the amplifier circuit board diagram is and how it works. Almost all the electronic equipment out there has to include some amplifying means for the signals. The application of the amplifier circuit board diagram can be seen in scientific equipment, medical devices, military tools, automation, communication devices, as well as household equipment. Aside from the main or basic types, amplifiers come in several types. This is grouped by their characteristics, application or operation.




                Get Fast Quote Now