Hi Guys

How can I have an amplifier with :

1- High gain
2- High input resistance
3- Low output resistance

Is it important to use multistage amplifier ??

 

How high is the gain?

What is the maximum operating frequency?

 

The input signal is 10mV

and the needed gain is 40V/V

The frequency is 1000Hz= 1khz

 

You can use an op amp in this case with good results.

 

You can use an op amp in this case with good results.

I should use BJT's or MOSFET's only !!!

 

Thank you for your response

 

Then you have to build a common emitter amplifier with a gain of 40V/V and then fed its output to the input of an emitter follower to achieve low output impedance.

 

Hello,

So you need a gain of 40 V/V.
What input resistance is required?
What output resistance is required?

Greetings,
Bertus

 

Hello,

So you need a gain of 40 V/V.
What input resistance is required?
What output resistance is required?

Greetings,
Bertus

Rin > 40k

Rout < 1k

 

Then you have to build a common emitter amplifier with a gain of 40V/V and then fed its output to the input of an emitter follower to achieve low output impedance.

Can you please show me the connection

because I tried this configuration (CE-CC) in the PSpice & the gain is approximately = 1

 

Thank you guys..I appreciate what you are doing

 

Hello,

That could be made with a two stage amplifier.
At the input a mosfet for the high input resistance and gain.
Afther that an emmitter follower for the low output resistance.

Greetings,
Bertus

 

Can you please show me the connection

because I tried this configuration (CE-CC) in the PSpice & the gain is approximately = 1

The gain of a CC is about 1.

The gain of a CE depends on Rc and Rin.

 

Hello,

That could be made with a two stage amplifier.
At the input a mosfet for the high input resistance and gain.
Afther that an emmitter follower for the low output resistance.

Greetings,
Bertus

Also CE will give a high gain & input resistance !!!

 

The rule says:

The gain of a multistage amplifier is the gain product of each BJT

 

So simply make a CE transistor with a gain of 40 followed by a CC transistor that has a gain of 1. The CE transistor has a high input impedance and the CC transistor has a low output impedance.

 

The rule says:

The gain of a multistage amplifier is the gain product of each BJT

This is true about the voltage gain.

For the current gain you cannot simply multiply the individual current gains.

 

This is true about the voltage gain.

For the current gain you cannot simply multiply the individual current gains.

You are absolutely right..