What characteristics make a circuit a good buffer?

[amjal422]

Buffer

I want to know what characterisitics make a circuit a good buffer,
1. What should be ideal values of input and output impedances of buffer. and how it effects the isolation of load form the other circuitry.
2. Can a buffer circuit should also provide gain to drive a high load.
3. Any other circuit in addition to common collector in Bipolar.


Thanks in advance

 

[sengyee88]

Re: Buffer

I want to know what characterisitics make a circuit a good buffer,
1. What should be ideal values of input and output impedances of buffer. and how it effects the isolation of load form the other circuitry.

Voltage buffer
High input impedance, to ensure it does not sink/source much current from previous stage and no much signal attenuation.
Low output impedance, to ensure no signal attenuation to next stage and able to source/sink more current with minimum headroom required.

Current buffer
Reverse of voltage buffer

2. Can a buffer circuit should also provide gain to drive a high load.

If it provides gain, it should not call buffer. High gain does not means high drivability.

3. Any other circuit in addition to common collector in Bipolar.

Common base - current buffer

 

[amjal422]

Re: Buffer

I am talking about voltage buffer. The characteristics explained by you refer to Common Collector Circuit which has large input impedance, small output impedance, voltage gain of aprroximate unity and some current gain.
This buffer provides power gain. So there is gain.
Why buffer is sometimes called as buffer/amplifier in literature?