PCB for MAT-04 VCA

keen at austin.ibm.com keen at austin.ibm.com
Fri Feb 28 19:04:37 CET 1997


I'm having mailer difficulty, so if this is garbled, bear with me.

In looking at the circuit for the apnote 105 VCA and reading the discussion
on MAT04's, matched and unmatched transistors, it occurred to me that the
matched transistors needed are in substantially the same configuration as
the upper three diff amps in a 1496 balmod. The 1496 has the lower diffamp
tied to that pesky set of linear current sources on the emitters, but the 
emitter terminals are brought out as the "gain set" terminals. 

I think that the lower current source terminals could be inactivated by 
tying the current set terminal to V-. Then the two emitters could be used 
for the lower diffamp emitters in the apnote 105 circuit. The transistors 
should be matched... right???



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