A friend from Canada ordered a pair of boards and I used the opportunity to test the newly arrived hybrid mu-follower (aka as gyrator) Rev08 PCBs. He will be using these boards in the 300B design posted here.
Tag: Rev08
Hybrid Mu-follower (aka Gyrator) Rev08 PCB Update
It’s been far too long since I last posted on this blog. With the limited spare time I’ve got these days, I concentrated in setting up the new workshop and system since we moved back to our place. I’m nearly there, so now it’s time to get back to work
I made some updates to the “gyrator” PCB. I’ll stop referencing it gyrator from now on, since the name is misleading. However, it got popular that way. Nevertheless, it’s a hybrid mu-follower circuit but if only if you take the output from the anode, it behaves like a “gyrator” from a frequency response perspective. If you’re interested in this circuit in more detail, please read the lecture I gave last year at ETF.18. You can download it from here.
Back to the board, here are the few changes made:
- Moved the trimpot P1 for easier fixing of the board with the M3 standoffs.
- Added a gate stopper resistor (R9) to avoid oscillation at low anode current (<10mA) when using high-gm MOSFETs in the lower position J4. This was evident with devices like BSH111BNK
- Added an LED (D4) indicator and a series resistor (R8) at the drain of M3. This enables indication of:
- Normal operation subject to value of R8
- Source current into load (e.g. like in A2 operation) subject to value of R8.
- Short output to ground. Depending on duration and current limitation of power supply, this may prevent damaging M3 MOSFET. Not guaranteed, but in some scenarios will work.
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