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Lets take a look on a linear amplifier

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Md Mubdiul Hasan:

--- Quote from: Kleinstein on September 13, 2019, 12:30:07 pm ---The voltage boost part is needed because the OP can not directly drive the +-85 V swing to derive the MOSFETs.
At lower supply voltage an OP my be suitable. Using C1815 and similar transistors suggests that the different circuit uses a much lower supply.

However the voltage boost stage as shown uses way to much current for the small transistors.

With Darlington transistors instead of the FETs the bias circuit should also be different. So chances are one would start all over and forget about the circuit shown.

--- End quote ---

You are helping me a lot!
Yeap, for this reason C1815 and A1050 is used.

--- Quote ---However the voltage boost stage as shown uses way to much current for the small transistors
--- End quote ---
.
Then what other ways we can get a good result here?


--- Quote ---With Darlington transistors instead of the FETs the bias circuit should also be different. So chances are one would start all over and forget about the circuit shown
--- End quote ---

I will be happy if you can post a general design what you have said.

Now lets come to the point, I am talking about the feedback amplifier 

1. My voltage and current amp circuit is slightly different.

2. In voltage amp, at OPA551, input signal has feed with reference to "ground". A series RC element like 1k, 1uF after that a 220k (one end grounded) are connected to " non- inverting" input. Also a 220k one end ground is conneted to"inverting" input. A parallel RC element 270k, 0.33uF(may be) is connected to feedback path. A10 ohm, 0.1 uF RC element in series also appears in the output of the amp! Output signal also has ground reference.

3. In current amp, at OPA551, input signal is feed with reference to " ground". A series RC element like 13k, 1uF after that a 1k ( one end grounded) are connected to " non inverting" input. Also a 1k single ended gound is also conneted to "inverting" input. A parallel RC element (4.7k and 47uF) is connected to feedback path. A 10 ohm, 0.1 uF RC element in series are also appears between the output of the amp! In this case 2 shunt element 5W 0.5 ohm are connected and grounded in output side. No reference ground output here!

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