In a surprise change from the usual topics discussed in this group, I'm posting a question about electronic design!
Win kindly reposted this enhanced schematic of an amplifier board I've been troubleshooting:-
My question relates to the voltage-to-current section which comprises 6 transistors plus various passive 'support' components. My previous experience is confined to discrete amplifier stages where each transistor is dc-isolated from its neighbours by coupling capacitors and consequently have easily determined biasing arrangements for each stage. This is very different as all 6 transistors are directly inter-related and inter-dependent (for example the collector output voltage(s) of one has to be compatible with the base input of the next and so on. Not only this, but their emitters all share series connections with their compliments. This kind of arrangement is a PITA to troubleshoot, as a problem with just one active device (or its 'supporting components') causes weird voltage readings among the other 5 as well. Anyway, it occurred to me it must have been an even bigger PITA to actually *design* such a beast in the first place, given all the inter- dependence of the bias and signal voltages which all have to be accommodated. What thought processes would the designer of this board have had to go through in order to come up with what is effectively a monolithic 6- transistor "stage" with all the multiple complications that go with it? Where does one even begin??