RC coupled Amplifier

RC coupling Amplifier is also known as resistance-capacitor coupling Amplifiers.

●Circuit explanation :-

We know that , in RC coupling two stage Amplifier has two transistor,the both transistor connected according to shown circuit diagram , before you read about RC coupling Amplifier first you should see the circuit diagram.

You can see in shown figure , the RC coupled two stage Amplifier devided in two parts , in first part , capacitor C1 connected in series sequence between input terminal and Base of transistor Q1 , and the capacitor Ce connected between Emitter of Transistor Q1 and ground .

Similarly another capacitor Ce in stage two is connected .

....one think is important in this circuit diagram..a capacitor Cc is connected between collector to transistor Q1 and base of Transistor Q2 . And connection of Resistance's is shown In figure , we can design a two stage RC coupling Amplifier according to circuit diagram...

In two stage RC coupling Amplifier the capacitor Cc is connected between collector of one transistor and Base of another transistor is known as coupling capacitor

●Frequency Response In RC coupled Amplifier:-

Before the know about theory of RC coupled Amplifier Characteristics ( Frequency response) , we will do observe the curve of Frequency response.
The Curve of Frequency response shown in bellow ...

You have seen , this curve is showing relation between Frequency (f) and voltage gain (dB)

By using this curve we can define three conditions of Frequency response in RC coupled Amplifier .-

1. At low frequency , it means up to 50Hz the voltage gain is increases with Frequency .

2. More then 50Hz and up to 20KHz the voltage gain will remain constant , it means the Bandwidth of two stage RC coupling Amplifier is between 50Hz to 20KHz .

3. At high frequency , means more then 20KHz the voltage gain will decrease

"After studied Frequency response curve of two stage RC coupling Amplifier we can say that , RC coupled Amplifier work properly between 50Hz to 20KHz , it Bandwidth of two stage RC coupling Amplifier is 50Hz to 20KHz

● Working of two stage RC coupled Amp :-

You must have seen that in circuit diagram of Two stage RC coupled Amplifier following electronic element's -

Capacitor c1 , Ce , Co Cc
Resistor R1 , R2 , Rc Re
Transistors Q1 , Q2

We know that , the capacitor does not allow to pass DC Current it only allow to pass AC current , when input signal applied on transistor Q1 then capacitor C1 blocks DC Current it's allowed only AC current and Resistor R1 and R2 are used to provide proper biasing to a bipolar transistor Q1 and transistor Q2 , R1 and R2 provide Base voltage to Drive transistor Q1 and transistor Q2 in Active region.
We know that , the bipolar transistor works in three region , cut off region , Active region , saturation region !! , In cut off region bipolar transistor completely switched off . And the region where bipolar transistor completely switched on known as saturation region , the region between cut off region and saturation region is known as active region.

When , the input signal applied on input terminal of two stage RC coupling Amplifier then this signal is pass by capacitor C1 , the capacitor C1 allowed only AC component of input signal . This input signal is applied on base terminal of transistor and resistance R1 and R2 are provided proper biasing of Transistor Q1 and transistor Q2 , input signal is amplified by first stage , the amplified signal got by stage first , is input signal for stage second , in circuit of two stage RC coupled Amplifier capacitor Cc is connected between transistor Q1 and transistor Q2 is known as coupling capacitor , the coupling capacitor allowed on AC current in output of first stage and blocked DC component of signal and again amplify the signal by stage two , two stage RC coupled Amplifier is basically Amplifier device , it is use to amplifying the input signal , the input signal may be , power supply , voltage input , signal input by generating function !!

●Basic parameter of Transistor Amp:-

A good Amplifier must have following parameter:

It should have high input impedance
It should have high gain
It should have high Bandwidth
It should have high efficiency
It should have high stability

Stability:-
Stability is capacity of resist oscillation in amplification, generally stability problem occurs near high frequency , near 20 KHz in audio Amplifiers.

Gain:-
Gain is define by ratio of output signal and input signal , gain can be define in dB or number's . Gain is represent the ability of Amplify the signal .

Gain = output signal / input signal

Gain in dB = log10(output signal / input signal )

Gain is also expressed in voltage and current