Anyone seen Rush pairs used like this?
It is balanced in and balance out. Could be unbalanced in (by grounding one input) or a phase splitter (one input grounded and two output each wrt common).
Unlike the normal Circlotron this one has voltage gain, effectively common source.
Like a normal Circlotron it is symmetrical so even harmonics cancel. The p-channel and n-channel differences cancel -- you don't need to use well matched complements to get low 2nd harmonic distortion.
It can be biased for Class-A or Class-AB. In Class-A it approximates square-laws so the bias current can be about half that of standard push-pull Class-A with smaller heatsinks and transformers and caps. It can be used as a no feedback amplifier with current drive output.
In Class-AB there is an optimum bias for minimum crossover distortion, it is quite high bias (since there are no source resistors) giving low distortion over the first watt. It can be used as a no feedback amplifier with current drive output. The attached plot is with 300mA bias and 25V supplies giving about 0.01% THD at 1W/8R.
The bias current for Class-A or Class-AB needs to be stabilized with Vbe 2 multipliers (or thermistors) to prevent thermal runaway.
Best wishes to all here for 2020 and beyond.
Cheers,
It is balanced in and balance out. Could be unbalanced in (by grounding one input) or a phase splitter (one input grounded and two output each wrt common).
Unlike the normal Circlotron this one has voltage gain, effectively common source.
Like a normal Circlotron it is symmetrical so even harmonics cancel. The p-channel and n-channel differences cancel -- you don't need to use well matched complements to get low 2nd harmonic distortion.
It can be biased for Class-A or Class-AB. In Class-A it approximates square-laws so the bias current can be about half that of standard push-pull Class-A with smaller heatsinks and transformers and caps. It can be used as a no feedback amplifier with current drive output.
In Class-AB there is an optimum bias for minimum crossover distortion, it is quite high bias (since there are no source resistors) giving low distortion over the first watt. It can be used as a no feedback amplifier with current drive output. The attached plot is with 300mA bias and 25V supplies giving about 0.01% THD at 1W/8R.
The bias current for Class-A or Class-AB needs to be stabilized with Vbe 2 multipliers (or thermistors) to prevent thermal runaway.
Best wishes to all here for 2020 and beyond.
Cheers,
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