Kevin Weddle
- Feb 23, 2004
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A regulator that will produce both a postive and negative voltage will utilize a charge pump circuit. A charge pump circuit can be found in the electronic projects ideas page 3 section under negative charge pump. After that, you can build your own regulator. There is a simple one in the forum. I will find the link for you.
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Kevin Weddle
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Here is your regulator. Make sure the gain is one of the bottom transistor. Set the resistors to give you 5.7 at the base of the top transistor.
View attachment 36624
View attachment 36624
audioguru2
- Apr 6, 2004
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Hi Kevin,
I am sorry to say that your simple circuit is not a voltage regulator. Its output voltage will change with load current changes and temperature changes. It doesn't even have a voltage reference, like a biased-from-the-9V zener diode instead of the lower transistor's emitter resistor. That emitter resistor causes the lower transistor to have loss, instead of gain. :
Why not use an inexpensive voltage regulator IC like a 7805 instead? Its regulation is superb and it even has current-limiting if the load is shorted or attempts to draw too much current. It also has over-temperature protection, if it gets too hot it simply turns-off until it has cooled. ;D
I am sorry to say that your simple circuit is not a voltage regulator. Its output voltage will change with load current changes and temperature changes. It doesn't even have a voltage reference, like a biased-from-the-9V zener diode instead of the lower transistor's emitter resistor. That emitter resistor causes the lower transistor to have loss, instead of gain. :
Why not use an inexpensive voltage regulator IC like a 7805 instead? Its regulation is superb and it even has current-limiting if the load is shorted or attempts to draw too much current. It also has over-temperature protection, if it gets too hot it simply turns-off until it has cooled. ;D
audioguru2
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Hi Npatel,
Why do you need positive and negative supplies?
If it is for an audio amp, simply use a bridged audio amp IC. It uses a single supply like your 9V one and effectively doubles the voltage across the load for up to 4 times more power output. A bridged amp also doesn't need a large output coupling capacitor. ;D
Why do you need positive and negative supplies?
If it is for an audio amp, simply use a bridged audio amp IC. It uses a single supply like your 9V one and effectively doubles the voltage across the load for up to 4 times more power output. A bridged amp also doesn't need a large output coupling capacitor. ;D
Kevin Weddle
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Hello Audioguru. I did some searching and found some interesting regulators. There exists a circuit similiar to mine. Try it out.
http://www.northcountryradio.com/PDFs/column002.pdf
http://www.northcountryradio.com/PDFs/column002.pdf
audioguru2
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Hi Kevin,
I made simple regulators like that about 40 years ago.
The transistor regulator has my recommended "biased-from-the-9V zener diode instead of the lower transistor's emitter resistor" as a voltage reference. To make a 5V supply it would need a low-voltage voltage-reference IC or zener diode. Low voltage zener diodes don't regulate very well.
View attachment 36625
I made simple regulators like that about 40 years ago.
The transistor regulator has my recommended "biased-from-the-9V zener diode instead of the lower transistor's emitter resistor" as a voltage reference. To make a 5V supply it would need a low-voltage voltage-reference IC or zener diode. Low voltage zener diodes don't regulate very well.
View attachment 36625
Kevin Weddle
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Why do you recommend the zener in it's postion. I find the zener unnecessay. The voltage will rise at the base and produce current. The voltage will fall at the base of the pass transistor. The only function of the zener is to maintain a reasonable bias should the voltage of the out put drastically change. In fact the zener is biased from the input should the output voltage fall drastically.
audioguru2
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Kevin,
The zener is the circuit's voltage reference. The 2N3904 transistor compares the divided output voltage to the zener voltage, amplifies the difference and drives the power transistor to correct any change.
Also, the zener provides a low impedance to the emitter so the 2N3904 transistor can have voltage gain.
The zener is the circuit's voltage reference. The 2N3904 transistor compares the divided output voltage to the zener voltage, amplifies the difference and drives the power transistor to correct any change.
Also, the zener provides a low impedance to the emitter so the 2N3904 transistor can have voltage gain.
Kevin Weddle
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Audioguru, please give me some more info. As I understand it, the voltage across the PN of the 3904 is what changes. The zener does not regulate the output. It only regulates the emitter voltage.
audioguru2
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Kevin,
Of course the zener helps regulate the output voltage. It holds the voltage at the emitter constant so the transistor can amplify the difference between it and a divided-down sample of the output at its base.
In your circuit with a resistor instead of a zener, the emitter voltage followed the output voltage so the transistor couldn't amplify. It also didn't have a reference voltage for comparison.
Of course the zener helps regulate the output voltage. It holds the voltage at the emitter constant so the transistor can amplify the difference between it and a divided-down sample of the output at its base.
In your circuit with a resistor instead of a zener, the emitter voltage followed the output voltage so the transistor couldn't amplify. It also didn't have a reference voltage for comparison.
A
Alun
- Jan 1, 1970
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Want an easy to build bridge audio amplifier?
Try this chip: http://www.electronics-lab.com/forum/attachments/PH_TDA7052.pdf
Try this chip: http://www.electronics-lab.com/forum/attachments/PH_TDA7052.pdf
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audioguru2
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Hi Alun,
When I clicked on your bridged-amp attachment, Adobe asked if I wanted to download their new version 7.0, so I did. Thanks.
Ahh, just a whopping 1W from that little amp?
Here's a nice monster bridged-amp IC with a built-in power supply voltage doubler. Operating in class-H (it doubles the supply voltage only when the signal requires it), it gives 70W to a 4 ohm speaker from a 14.4V car battery! http://www.semiconductors.philips.com/acrobat/datasheets/TDA1562Q_ST_SD_2.pdf
When I clicked on your bridged-amp attachment, Adobe asked if I wanted to download their new version 7.0, so I did. Thanks.
Ahh, just a whopping 1W from that little amp?
Here's a nice monster bridged-amp IC with a built-in power supply voltage doubler. Operating in class-H (it doubles the supply voltage only when the signal requires it), it gives 70W to a 4 ohm speaker from a 14.4V car battery! http://www.semiconductors.philips.com/acrobat/datasheets/TDA1562Q_ST_SD_2.pdf
