What is unity gain?

[Syafiq]

What is a unity gain? I understand that it is a gain of 1 or 0dB, but how is it applied in audio applications? Thanks

 

[crutschow]

If you want to drive a low impedance load from a high impedance source without voltage amplification then you would use a unity gain amplifier.

 

[WTP Pepper]

Unity gain tends to refer to the voltage gain. You can have unity gain in a power amp as it can still have current, thus power gain.
BTW Unity voltage gain is a gain of 1 (1 volt in and 1 volt out). In dBs, it's 0dB as 20 x log (1) = 0.

 

[JimB]

Unity gain tends to refer to the voltage gain. You can have unity gain in a power amp as it can still have current, thus power gain.
BTW Unity voltage gain is a gain of 1 (1 volt in and 1 volt out).

I agree with that, but I would like to point out that the following statement is a bit iffy, verging on totally wrong.

In dBs, it's 0dB as 20 x log (1) = 0.

The deciBel is defined as the ration of two POWERS.
If we wish to calculate the dB gain using voltages, we must either make sure that the impedance of the input and output of the system are the same, or we must account for the impedance difference by using the expression
dB = 10 x Log(V2 x V2 /R2)/(V1 x V1 /R1)
effectively calculating the input and output powers.

If an amplifier has current gain but no voltage gain, it still has power gain.

JimB

 

[crutschow]

I agree with that, but I would like to point out that the following statement is a bit iffy, verging on totally wrong.

In dBs, it's 0dB as 20 x log (1) = 0.

The deciBel is defined as the ration of two POWERS.
.............................

That's true by definition. But it is common (though not technically correct) to refer to voltage gain in dB as 20 log (Vo/Vin) even when the input and output impedances are different.

 

[KeepItSimpleStupid]

JimB:

If an amplifier has current gain but no voltage gain, it still has power gain.

Assume "A"=gain

Ambiguous: Take no to mean 0 or take no to mean 1. 0*A = 0 power gain;
Voltage of 1 is still gain. So, so is a gain of 0.1 gain or no gain? Otherwise we get this piecemeal discontinuous function at A=1, I don't think so.

 

[WTP Pepper]

If an amplifier has current gain but no voltage gain, it still has power gain.

JimB

I am not disputing that. I said as much in my OP.