If I put my notes here, I might be able to find them again later!
Voltage regulators for (line level?) audio: The GeminiPS
Part of a series.
The GeminiPS is another discrete series voltage regulator, with a Zener reference and bipolar pass transistor. It's an old circuit, published in Practical Electronics in 1970-71, and written by D.S. Gibbs and I.M. Shaw. I happen to have a reprint, but there's a nice overview here.
For reference it might be worth checking back to the two transistor regulator. The GeminiPS circuit is related in the sense that it is a more sophisticated take on the same basic principle. With just a handful of components we have a stabilized, 30 W output with soft turn on and short circuit protection. The circuit can be scaled up and down relatively easily, and the complimentary (negative output) version is an easy modification.
The pass transistor (TR2/3, Q2/3) is between the circuit common and the rectifier anodes. This may seem odd, but it was relatively common back in the day when high voltage transistors were both expensive and rare. The idea is to put as much of the delicate circuitry on the low voltage side as possible. It's not foolproof, but it's better than the (now) conventional position on the high voltage side.
The output voltage is adjusted by VR1 in the circuit, or the ratio R1,R2 in the LTSpice sim. R5 controls the maximum output current before the clamping effect turns on. The soft-start rise time is controlled by R3,C2. You can see in the LTSpice simulation shown below, turn on and turn off sequences are free from peaks and oscillation and complete in about 1 second.
The GeminiPS is another discrete series voltage regulator, with a Zener reference and bipolar pass transistor. It's an old circuit, published in Practical Electronics in 1970-71, and written by D.S. Gibbs and I.M. Shaw. I happen to have a reprint, but there's a nice overview here.
For reference it might be worth checking back to the two transistor regulator. The GeminiPS circuit is related in the sense that it is a more sophisticated take on the same basic principle. With just a handful of components we have a stabilized, 30 W output with soft turn on and short circuit protection. The circuit can be scaled up and down relatively easily, and the complimentary (negative output) version is an easy modification.
The pass transistor (TR2/3, Q2/3) is between the circuit common and the rectifier anodes. This may seem odd, but it was relatively common back in the day when high voltage transistors were both expensive and rare. The idea is to put as much of the delicate circuitry on the low voltage side as possible. It's not foolproof, but it's better than the (now) conventional position on the high voltage side.
The output voltage is adjusted by VR1 in the circuit, or the ratio R1,R2 in the LTSpice sim. R5 controls the maximum output current before the clamping effect turns on. The soft-start rise time is controlled by R3,C2. You can see in the LTSpice simulation shown below, turn on and turn off sequences are free from peaks and oscillation and complete in about 1 second.
Total Comments 2
Comments
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Deleted - was nonsense
Posted 22nd April 2014 at 11:18 AM by jan.didden
Updated 22nd April 2014 at 11:21 AM by jan.didden -
Replace the Zener with a series string of a 8.2V Zener and a red LED for 2x better temperature drift. Using two 4.7V Zeners and a 1N4004 in series is even 7x better; that is only 0.2V output drift from 30°C to 100°C (simulated).Posted 23rd April 2014 at 11:14 AM by Preamp
