Ic Vs Discrete

AR1 · 28th April 2005, 09:26 PM

Most of the power amplifier designs I have been looking at use discrete circuits in the input stage. The can get quite elaborate when designing for hi PSRR. Is their a reason why OP Amps are not more commonly used in these applications?

Mr Evil · 28th April 2005, 10:40 PM

I can think of a few reasons:

Voltage rating. Op-amps are generally not commonly available at >+/-25V or so.
Stability. op-amps already contain 3 or more stages, so adding extra stages after that makes stability less easy to obtain.
They're too easy! Where's the fun in just using an op-amp?

But still, I have seen plenty of excellent power amps with op-amp input stages, and I've made a few that worked pretty well too.

EchoWars · 29th April 2005, 03:11 AM

Quote:

Originally posted by Mr Evil
They're too easy! Where's the fun in just using an op-amp?

That's the biggest reason...

Good for beginners I suppose, but any real DIY'er ought to get beyond them quickly.

HFGuy · 29th April 2005, 03:24 AM

After much consideration about discrete vs IC i have made a choice. I will impliment my BlueTooth transceiver in 90nm CMOS rather then discrete

. ICs have many advantages but most thoses advantages dont apply to audio frequencies.

AR1 · 29th April 2005, 02:09 PM

Yes I can see your point. But their are many Hi quality op amps that are very stable, they reduce part count and if integrated properly in the topology they make an excellent choice for manufacturing. Not to mention the reduction in complexity, the large variation in discrete component specs, and ease of troubleshooting and repair.

I own an old Carvin FET 1000 amp that utilize opamps in the front end of their amplifier. I also wondered how they dealt with the large discrepancy in supply voltages. It seems they incorporate resistive networks to reduce the voltage in the NFL to reduce the voltage swing at the input of the opamp. I have to assume there is a trade off in terms of gain, but all I can say it the amp is rock solid and in all the years I have had it never given me any problems and it performs admirably!

In closing I would have to say I also favor conventional discrete circuits.

28th April 2005, 09:26 PM	#1
AR1 diyAudio Member Join Date: Mar 2005 Location: New York	Ic Vs Discrete Most of the power amplifier designs I have been looking at use discrete circuits in the input stage. The can get quite elaborate when designing for hi PSRR. Is their a reason why OP Amps are not more commonly used in these applications?

28th April 2005, 10:40 PM	#2
Mr Evil diyAudio Member Join Date: Aug 2004 Location: Behind you	I can think of a few reasons: Voltage rating. Op-amps are generally not commonly available at >+/-25V or so. Stability. op-amps already contain 3 or more stages, so adding extra stages after that makes stability less easy to obtain. They're too easy! Where's the fun in just using an op-amp? But still, I have seen plenty of excellent power amps with op-amp input stages, and I've made a few that worked pretty well too. __________________ https://mrevil.asvachin.eu/

29th April 2005, 02:09 PM	#5
AR1 diyAudio Member Join Date: Mar 2005 Location: New York	Production Yes I can see your point. But their are many Hi quality op amps that are very stable, they reduce part count and if integrated properly in the topology they make an excellent choice for manufacturing. Not to mention the reduction in complexity, the large variation in discrete component specs, and ease of troubleshooting and repair. I own an old Carvin FET 1000 amp that utilize opamps in the front end of their amplifier. I also wondered how they dealt with the large discrepancy in supply voltages. It seems they incorporate resistive networks to reduce the voltage in the NFL to reduce the voltage swing at the input of the opamp. I have to assume there is a trade off in terms of gain, but all I can say it the amp is rock solid and in all the years I have had it never given me any problems and it performs admirably! In closing I would have to say I also favor conventional discrete circuits.

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29th April 2005, 03:24 AM	#4
HFGuy diyAudio Member Join Date: Sep 2004 Location: Toronto, Ontario	After much consideration about discrete vs IC i have made a choice. I will impliment my BlueTooth transceiver in 90nm CMOS rather then discrete . ICs have many advantages but most thoses advantages dont apply to audio frequencies.

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