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Old 7th July 2013, 04:46 PM   #9241
smms73 is offline smms73  Portugal
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One way or another, I have already made a lot of modifications at the circuit from post #9211 , now the voltage reference is feed by the output voltage insted of the input voltage (Frans suggestion), now the PSRR is even higher.
And now I have two versions one is a shunt other is a serial regulator. The serial regulator also has very good PSRR better than 130dB at audio frequencies.
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Old 7th July 2013, 05:21 PM   #9242
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I also have bought some so-8 biss transistors to test, but haven't done that yet. I guess the bc857c has low parasitic capacities enough for this application. Have to buy some caps , will buy some transistors also, for this.
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Old 7th July 2013, 05:46 PM   #9243
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The important of the square wave test is to see anomalous behavior of the regulator. Some of these circuits have lots of gain and lots of BW but low slew rate, and so saturate and go nuts when you actually try to use them at the expected BW.

Last time I looked I liked the PEMZ7 from NXP.
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Old 7th July 2013, 06:08 PM   #9244
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I was expecting to see some spikes at the turn on and off of the current , but as the HEC loop is faster ,maybe is because of this the reason for the absence of those abnormalities. I have to investigate futher .

I was thinking in less than 2pf collector capacitance, but thanks . NXP has nice transistors.

I will try use the bc550 just to test as I have lots of them. If the stability of the regulator stays good, I will use them.
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Old 8th July 2013, 11:25 PM   #9245
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Today I made a test PCB of the regulator. Maybe tomorrow will be done ... Maybe.
Attached Images
File Type: png HECshunt_pcb.png (34.0 KB, 121 views)
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Old 8th July 2013, 11:31 PM   #9246
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cool, nice work you do.
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Old 8th July 2013, 11:32 PM   #9247
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Can you make a 5 V version of this ?
I need around 60mA.
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Old 8th July 2013, 11:43 PM   #9248
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No problema. To have 5v, is only need to change the value of two resistors. But first lets see if it works as planned. tomorrow will etch a pcb.
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Old 9th July 2013, 12:01 AM   #9249
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Ok, fine.
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Old 9th July 2013, 12:26 AM   #9250
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I build another buffer.
This time the Mr. Evil Diamond Fet Bootstrap.
Pictures and measurements soon.
I wanted to compare it to the Piglets Dad.
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