simple GCSS

[Leolabs]

Any comment???

[Leolabs]

Just wondering:

1)Will it remain stable owe to such simple design???

2)Still need high driving capability preamp???

[metalman]

1)Will it remain stable owe to such simple design???

Topologically speaking, it's identical to circuit I've refined in the GC Supersymmetry thread, the only difference being that you're using one dual op-amp LM4780 chip where I've used two LM3875 chips. So stability shouldn't be a problem as long as you deal with the gain issue correctly. To achieve stability you'll have to adjust the ratios of R9:R10 and R14:R15 to throw away some of the open loop gain, and perhaps increase R7 and R8. If you have a look at the recent schematic I've posted near the end of the GC Supersymmetry thread, you can get some ideas of where the values may lie.

2)Still need high driving capability preamp???

The need for some drive at the input comes from the fact that you're driving into a bipolar transistor (a current gain device) through only a 1K resistor. So your circuit hasn't defeated this issue.

Cheers, Terry

[Leolabs]

Thanks for the advices,meta

[Nicke]

Originally posted by metalman


The need for some drive at the input comes from the fact that you're driving into a bipolar transistor (a current gain device) through only a 1K resistor. So your circuit hasn't defeated this issue.

Cheers, Terry

Have you tried to use a pair of JFETs instead?
Then it would perhaps be possible to use a pair of 10kohm resistors at the input and 220kohm as feedback resistors.