Help with active filters - Electronic Circuits Projects Diagrams Free

Mothra · 17th April 2008, 02:21 PM

Hello,

I am currently in college and working on a final project. It is a 5-channel color organ made up of 5 active filters (opamp sallen-key filters to specify). This may seem like a stupid question but if these filters are of unity gain, do the opamps need a DC supply voltage? If so, how do I determine the DC supply voltage to use?

Thanks in advance

ronsimpson · 17th April 2008, 03:33 PM

The supply voltage needs to be greater than the signal P-P. Most amplifiers cannot pull their outputs to the + and – supply pins. If your signal is 5 volts pk or 10 volts p-p then the amplifier needs 3 volts head room so you need +8 volts and –8 volts minimum. If your signal is AC coupled and is centered around ½ supply then you need 16 volts of supply.

Do op-amplifiers (with a gain of 1) need a supply voltage?
Does your car need a motor to go on a flat road?
Gain of 2 = uphill.
Gain of 0.5 = down hill. (keep the motor running)

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17th April 2008, 02:21 PM	(permalink)
Mothra	Help with active filters Hello, I am currently in college and working on a final project. It is a 5-channel color organ made up of 5 active filters (opamp sallen-key filters to specify). This may seem like a stupid question but if these filters are of unity gain, do the opamps need a DC supply voltage? If so, how do I determine the DC supply voltage to use? Thanks in advance

17th April 2008, 03:33 PM	(permalink)
ronsimpson	The supply voltage needs to be greater than the signal P-P. Most amplifiers cannot pull their outputs to the + and – supply pins. If your signal is 5 volts pk or 10 volts p-p then the amplifier needs 3 volts head room so you need +8 volts and –8 volts minimum. If your signal is AC coupled and is centered around ½ supply then you need 16 volts of supply. Do op-amplifiers (with a gain of 1) need a supply voltage? Does your car need a motor to go on a flat road? Gain of 2 = uphill. Gain of 0.5 = down hill. (keep the motor running)