Can anyone point me to some relevant reading on choosing operating points when applying CCS's to small signal tubes?
I know how to read a curve chart and choose an OP based on B+, plate resistor, grid bias, etc, but I'm not sure how to go about this with a CCS. Is it as easy as figuring the current draw through the CCS, the grid bias, and letting it operate right at B+? Do I still need some resistive loading on the plate?
Backstory: have 100V B+ and was thinking about how to maximize the voltage
I know how to read a curve chart and choose an OP based on B+, plate resistor, grid bias, etc, but I'm not sure how to go about this with a CCS. Is it as easy as figuring the current draw through the CCS, the grid bias, and letting it operate right at B+? Do I still need some resistive loading on the plate?
Backstory: have 100V B+ and was thinking about how to maximize the voltage
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Choosing the operating point for a small signal stage with a CCS in the cathode is exactly the same as for a normal stage. You still put a load line based on anode load and supply rail voltage. The only difference is that you don't have to calculate a cathode resistor, just designa a CCS to give the required quiescent current - it sets the effective grid voltage to match the particular valve sample. Whether a bypassed CCS is better or worse than using a bypassed resistor is a moot point - a resistor is certainly cheaper and more reliable.
With limited supply voltage you can maximise the anode voltage by using a good anode load CCS, not a cathode CCS.
With limited supply voltage you can maximise the anode voltage by using a good anode load CCS, not a cathode CCS.
Sorry to bump an old thread but I read somewhere that depending on the cathode voltage you need to add a small B- supply? How does this work? I have a design idea but the bias voltage is 1.5V but I know that it needs at least 1.25V across it to function. Would I add a small resistor to the tail and connect it to a -5V supply?
No, you just connect the presumably CCS with 1.25v min working voltage across the cathode and -5V supply, no resistor necessary. This provides 1.5v+5v-1.25v headroom for the CCS.
Thank you. That was my assumption but I wanted to clarify. Cheers.
Draw a diagram of what you are thinking about, as your prose does not make enough sense to answer. Clarify what you mean by "it" and "tail".
Ballpencil seemed to have no problem understanding my prose, and he's from Indonesia. For the record "it" in this context meant "CCS" and "tail" meant the cathode.
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Ballpencil seemed to have no problem understanding my prose, and he's from Indonesia. For the record "it" in this context meant "CCS" and "tail" meant the cathode.
Somewhat mean response to someone trying to help you, especially since your post wasn't clear to me when I read it either.
Somewhat mean response to someone trying to help you, especially since your post wasn't clear to me when I read it either.
Sorry not trying to be mean at all. Seeing as this is a thread about a CCS in the cathode I though it was clear enough.
We had a lecturer who was Russian, who spoke poor English with a heavy accent. Native English speakers struggled to understand him. Chinese students said they could understand him more easily than the native-English-speaking lecturers.kodabmx said:Ballpencil seemed to have no problem understanding my prose, and he's from Indonesia.
On another occasion, I heard an engineering lecturer in a lesser university ask a class what was the most general form of the sine function. I was puzzled; the answer was obviously 'sin z', where z can be almost anything (real, complex, a matrix etc.) but that would probably have gone over their heads. It turned out that what he was looking for was 'A sin (2 pi f t + phase)', which to me as a physicist was a very particular form of the sine function but I suppose to them it was the most general one they had seen.
At this point you had not mentioned a CCS, so 'it' could not have been referring to it; I can't see the context inside your head.For the record "it" in this context meant "CCS" and "tail" meant the cathode.
'Tail' never means cathode; it means (in certain circuits only) whatever is connected to the cathode.
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