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Old 14th July 2013, 10:35 AM   #31
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Same goes for ripple rejection...an RC filter causes roll-off at all frequencies above fc = 1/2pi*R*C. The higher the C and the R, the faster the roll-off...
I think I can relate this to a mechanical setting...
Think of the output voltage as a crank or a wheel set to a determined position. Any ripple or noise causes the crank to slightly wobble to left and to right. Now, the higher the C in the RC filter, the bigger the crank is, so "wobbles" have less impact on it's position - a big C responds slowly to voltage change. The higher the R, the harder is the crank to rotate, which suppresses the wobbling further. But, the higher the R, the harder it is to set the output voltage (rotate the crank to a position, or charge the output capacitor), and output current - which goes for output impedance. Same thing goes for the crank size - a crank with higher diameter rotates easily, or the bigger C size gives less output impedance - but only until it discharges, or the crank goes to full position. It's a crude way to explain, but that's how I got the idea after some thinking
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Old 15th July 2013, 04:33 AM   #32
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There is a shunt regulator used in RMI FC100, which goes un-noticed as it is not a stand alone psu post. Anyone SIMed it.

Gajanan Phadte
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Old 3rd August 2013, 04:05 AM   #33
tjencks is offline tjencks  United States
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Guys sorry I dropped off this thread for a bit. I think I'm going with the Jung shunt. Downloaded a bunch of articles I need to read first though. What would folks suggest as a first step. Identify the parts or should I go with what Jung recommends in his last article not on the shunt version but the standard Jung Super Reg.

Just acquired an HP 35665A with full feature set enabled from John Bau of Precision Services. Excellent price...so have a bunch of reading to do on understanding how to use the FFT to look at different aspects of the power supply and my amps.
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Old 3rd August 2013, 03:37 PM   #34
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Quote:
Originally Posted by tjencks View Post
Guys sorry I dropped off this thread for a bit. I think I'm going with the Jung shunt. Downloaded a bunch of articles I need to read first though. What would folks suggest as a first step. Identify the parts or should I go with what Jung recommends in his last article not on the shunt version but the standard Jung Super Reg.
It's easy enough to modify the series regulator to the shunt. I don't think you can make an a priori decision -- try both and see which actually sounds better.
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Old 3rd August 2013, 04:54 PM   #35
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I'd suggest you arrange the circuit (shunt or series) so there's at least 3 mA of dc current flowing into the opamp's output pin; this (1) keeps you away from opamp crossover nonlinearities, and (2) operates the Jung level shifter at a reasonable current.

In the Jung AX interview article's schematic, (VBE / RB) sets the dc current flowing into the opamp output, and D8+C5 perform the level shift function.

Since your output current demand is so low, you could install a lower power, higher fT pass transistor like the 2SA1930 in the QPNP position. Whereas Jung's D45H11 specs are 10 amps & 70 MHz, the 2SA1930 is spec'd at 2 amps and 200 MHz.
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