gary pimm's latest self-biasing CCS circuit

[jarthel]

here's the page: http://home.pacifier.com/~gpimm/self_bias.htm.

here's the schematic: http://home.pacifier.com/~gpimm/self_bias_ccs.gif

1. It talks about "reference voltage" and it is ranging from 9.5 to 27V. Is this reference voltage the voltage across C2?

2. Is the output coming out the "-" lead (after R1)? I have a feeling this is right but just want to confirm.

thanks for the help

[leadbelly]

Originally posted by jarthel
1. It talks about "reference voltage" and it is ranging from 9.5 to 27V. Is this reference voltage the voltage across C2?

I believe so.

Originally posted by jarthel
2. Is the output coming out the "-" lead (after R1)? I have a feeling this is right but just want to confirm.

Gary's CCS's are all "two-wire", which he confirmed to me in an email. So the output depends upon the application. If you're using the CCS for a plate load, then "-" is the output to the plate. If you're using the CCS for a long tailed pair, the "+" is the output to the cathodes.

[jarthel]

thanks for the help.

another question if you don't mind. how do I test the circuit (using it as a plate load) if I don't have a B+ supply.

in Bas Horneman's site (http://home.zonnet.nl/horneman/mosfet.htm), I can connect a 9V battery and a 10ohm resistor to check the circuit. But I believe the CCS is Bas' site is an older version.

I somehow have a feeling that this might not be possible with the latest circuit.

[leadbelly]

9V sounds low, but if you string a few in series you should be OK.

[jarthel]

Originally posted by leadbelly
9V sounds low, but if you string a few in series you should be OK.

same testing circuit as this http://home.zonnet.nl/horneman/image...urrent_set.gif
except that I have more than 9V? thanks again

[Rescue Toaster]

Depending on where you put R1 and how much current you're going for, the CCS will start to operate around 25-35v, though for large R1 & large R11 values, it can take more.

I assume your current is pretty low? Six 9v batteries in series should work. They won't last very long at 20-30ma for instance but you should be able to check that its working and trim the current.

[leadbelly]

Yes.

[jarthel]

Originally posted by Rescue Toaster
Depending on where you put R1 and how much current you're going for, the CCS will start to operate around 25-35v, though for large R1 & large R11 values, it can take more.

I assume your current is pretty low? Six 9v batteries in series should work. They won't last very long at 20-30ma for instance but you should be able to check that its working and trim the current.

I need 75mA. hmm maybe I do need a b+?

thanks again

[Rescue Toaster]

What R1 value did you choose?

Regardless, 6x 9v should cause it to turn on even with very large values of R1. Even good alkalines won't give you very long to test it though, so get it setup w/ your voltmeter across R1 already, and switch on. If you have to adjust R11 to an extreme to get it to 75ma, you probably need to change R10. Or you might have picked too large a value for R1.



vvv Sounds good. Unless you get unlucky with your mosfets you shouldn't have much trouble. You might be able to use only four 9v's to test but that gives pretty low Vds for Q2.

[jarthel]

Originally posted by Rescue Toaster
What R1 value did you choose?

200ohms