Misconceived definition of compensation
That definition of compensation is misconceived. Compensating an amplifier means simultaneously reducing the gain of each stage and modifying its frequency response to promote stability of the amplifier's major and/or minor feedback loops.
That definition of compensation is misconceived. Compensating an amplifier means simultaneously reducing the gain of each stage and modifying its frequency response to promote stability of the amplifier's major and/or minor feedback loops.
Emitter-coupled pair (series complementary or Long Tail Pair) can be arranged in
a few different ways:
■ Cascode: 1 AC input and 1 AC output.
Cascodes can be inverting or non-inverting, straight or folded.
And any ECP can be arranged to work even as Common "Emitter" + Common "Base"...
For any ECP it will be incorrect to call the Common Collector tr. "Em. follower" because
this tr. receives only 0.5 (and it can be even 0.3) of the input diff. voltage. With such
a low output (0.3...0.7) on it's Em. it doesn't qualify to be called a "follower" (0.9...0.95 ~1)
■ Differential amplifier: 2 inputs (both AC, or both DC) and 1 or 2 (accordingly AC,
or DC) outputs. There are also DC amplifiers, you know...
Differential amplifier responds to the difference of the two input signals in the same
domain.
Differential AC amplifiers can be balanced or unbalanced at the input and/or outputs.
And there is no such thing as "differential pair". "Differential" can be an amplifier.
■ Phase splitter: 1 or 2 AC inputs and 2 AC outputs.
And that pair will be called by the main function it performs in an amplifier.
For example: "Phase splitter based on the diff. amplifier".
In the NAD3020 RIAA amp the first stage is Diff. amp (series ECP), the second -
non-inverting folded cascode (with LTP =CC+CB).
a few different ways:
■ Cascode: 1 AC input and 1 AC output.
Cascodes can be inverting or non-inverting, straight or folded.
And any ECP can be arranged to work even as Common "Emitter" + Common "Base"...
For any ECP it will be incorrect to call the Common Collector tr. "Em. follower" because
this tr. receives only 0.5 (and it can be even 0.3) of the input diff. voltage. With such
a low output (0.3...0.7) on it's Em. it doesn't qualify to be called a "follower" (0.9...0.95 ~1)
■ Differential amplifier: 2 inputs (both AC, or both DC) and 1 or 2 (accordingly AC,
or DC) outputs. There are also DC amplifiers, you know...
Differential amplifier responds to the difference of the two input signals in the same
domain.
Differential AC amplifiers can be balanced or unbalanced at the input and/or outputs.
And there is no such thing as "differential pair". "Differential" can be an amplifier.
■ Phase splitter: 1 or 2 AC inputs and 2 AC outputs.
And that pair will be called by the main function it performs in an amplifier.
For example: "Phase splitter based on the diff. amplifier".
In the NAD3020 RIAA amp the first stage is Diff. amp (series ECP), the second -
non-inverting folded cascode (with LTP =CC+CB).
There are 2 signal paths. One is the cascode path, the other is the amplification path. The amplification path is so dominated that the cascode path is irrelevant and can be replaced with an independent current source. Thus, it is equivalent to single ended input stage with a VAS. Additionally, the feedback path is buffered with an emitter follower.