In this note, we are going to learn about RC Coupled Amplifier, about its circuit diagram, operation, advantages, disadvantages, and applications. Welcome to Poly Notes Hub, a leading destination for engineering notes for diploma and degree engineering students.
Author Name: Arun Paul.
About RC Coupled Amplifier
This is the most popular type of coupling because it is cheap and provides excellent audio fidelity over a wide range of frequency. It is usually employed for voltage amplification.
RC Coupled Amplifier Circuit Diagram
Fig shows two stages of an RC coupled amplifier. A coupling capacitor Cc is used to connect the first stage’s output to the second stage’s base and so on. As the coupling from one stage to next is achieved by a coupling capacitor followed by a connection to a shunt resistor, thereby, such amplifiers are called resistance -capacitance coupled amplifiers.
The resistance R1, R2 and RE form the biasing and stabilisation network. The emitter bypass capacitor offers low reactance path to the signal. Without it, the voltage gain of each stage would be lost. The coupling capacitor Cc transmits a.c. signal but blocks d.c. This prevents d.c. interference between various stages and the shifting of operating point.
RC Coupled Amplifier Working
Here is the working of RC Coupled Amplifier –
When an alternating current (AC) signal is delivered to the base of the first transistor, it is amplified across its collector load (RC). The amplified signal generated across Rc is routed to the base of the following stage via coupling capacitor Cc. The second stage further amplifies the signal. The cascaded stages enhance the signal, significantly increasing the overall gain.
It should be noted here that the total gain is smaller than the product of the gains from separate stages. It is because when a second stage is added after the first stage, the effective load resistance of the first stage decreases due to the shunting effect of the second stage’s input resistance. This lowers the gain of the stage loaded by the following stage. For example, in a three-stage amplifier, the gain of the first and second stages is reduced due to the loading effect of the next stage. However, the gain of the third stage, which has no loading effect on the following stage, remains constant. The overall gain shall be equal to the product of the gains of three stages.
Advantages of RC Coupled Amplifier
Here are the merits of this type of amplifier –
- It has excellent frequency response.
- The gain is not variable over the frequency range.
- It has a lower cost because this circuit has only resistors, capacitors, and transistors.
- The circuit is very compact in design.
Disadvantages of RC Coupled Amplifier
Here are the demerits of this type of amplifier –
- It has lower voltage gain.
- It has lower power gain.
- It has poor impedance matching.
Applications of RC Coupled Amplifier
Here are some uses of this type of amplifier –
- Used in Audio Amplifiers.
- Used in Voltage Amplifiers.
- Also used in Public Address Systems.