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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: Opamp class A bias using FET - how to calculate resistor value? posted by Saurav on May 3, 2002 at 11:08:54:
using Ibias ~ .56 mA from Risch's 2nd reference thread ( see post below ) this whole discussion is probably irrelevant to OPA2134OPAx134 data sheet gives open loop output impedance = 10 Ohm
from Zout = 1/2 * ( 26 mV / Ibias ) we can say output stage Ibias > 1.3 mA, unless they've used additional local feedback around the output stage transistors
also why FET constant current source? Bipolar source with vref diode or Wilson current sink can set Ibias to < 5% tolerance with no trimming required
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Follow Ups
- 1-2 mA Ibias for OPA134 ... coal to Newcastle? - jcox 22:10:45 05/06/02 (3)
- Re: OK, now I'm lost :) - Saurav 09:03:44 05/07/02 (2)
- Re: OK, now I'm lost :) - jcox 16:28:44 05/07/02 (1)
- Re: Thanks, that makes more sense (nt) - Saurav 17:33:40 05/07/02 (0)
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