I think going to 50R and 150R would move the offset about 20mV.
If turns out to be the case, then there's a fault in the circuit, or it's badly designed in the first place.
I think going to 50R and 150R would move the offset about 20mV.
If turns out to be the case, then there's a fault in the circuit, or it's badly designed in the first place.
It's a consequence of calculation and demonstrates that there is a problem with the circuit as realised which ought to be understood before tweaking.If turns out to be the case, then there's a fault in the circuit, or it's badly designed in the first place.
If Neil gives us the voltages around TR1, TR2, TR3 and TR4 perhaps the culprit will jump out...
OK, so just checked the HFE of the R1/R2 - it made no difference to the offset.
BUT thanks to Paul and Sparts - changed R1 out to 1.2K and the offset dropped to 49mV. Could this be the answer? And is there any harm in pushing just a little further to get well under the 50 limit?