Re: Copying Op Amps to Make Mic Amps



John Larkin wrote:

"Phil Allison" wrote:
"John Larkin"

With a typical voltage gain of 30 million and a typical gbw of 75 MHz,
the LT1028 should be pretty good. The data*** does have thd curves,
hitting numbers like 1 ppm at 1 khz, g=-20, 20 v p-p out. Not bad!

** Shame how that figure is not typical.

For the non inverting mode, with 600 ohms load, gain of 1000 ( as used in a
mic pre-amp ), frequency 20 kHz - the THD figure rises by 1000 times to
a mediocre 0.1%.


Sure. 75 MHz / 1000 is only 75 KHz of available gbw.

Which is where using op-amps exclusively falls down. I can't think of many
situations where I use them for > 30dB gain. Rarely above 20dB in fact.

Graham

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