Difference between op amp an power amp

[e44-72]

Hello

What is the difference between an ordinary operational amplifier (such as a 741) and a power amp ic (such as the LM386).

Both have inverting and non-inverting inputs, so whats the main difference?

thank you for any replies.

 

[KeepItSimpleStupid]

I'm going to take you to a website whose company specialized in power op amps. To give you an idea of their capabilities, 50 Amps output and 1200 V supply voltages. They are expensive.

IC Opamps that your familiar with may operate to 30 V and a few mA of output.

I have an audio amplifier that is layed out as an OP amp. Again +-50 V power rails and 3 Amp of output.

The biggest difference is cost. They just have different goals. One might be low bias currents, another low Vos, another Low quiesent currents etc.

 

[ronsimpson]

Both have inverting and non-inverting inputs, so whats the main difference?

A car and a big truck have a break and a gas pedal, so whats the difference?

 

[KeepItSimpleStupid]

You have to double clutch an 18 wheeler. I know, my cousin let me take a fully loaded one around a parking lot when I was about 20 YO. Scarey, but a valuable experience. Very valuable.

 

[audioguru]

The 741 has inputs that must be close to half the DC supply voltage.
The LM386 has inputs that work at its negative supply voltage that is usually 0V (ground).

The 741 has a max output current of about 20mA so it can drive a load of 2000 ohms.
The LM386 has a max output current of about 810mA so it can drive an 8 ohm speaker.

The 741 needs negative feedback resistors added.
The LM386 has built-in negative feedback resistors.

The 741 has trouble above 9kHz.
The LM386 works well to 300kHz.

 

[Nigel Goodwin]

You have to double clutch an 18 wheeler.

I suspect that's only on very old trucks

 

[unclejed613]

if you look at the "equivalent circuit" diagram on an op amp's data sheet, and compare it to a power amp, you will find them very similar. if i were to design a discrete op amp, it would be very similar to a power amp design, except for the output stage, which would be just two small transistors for the op amp, but as many as 3 pairs of successively larger transistors (usually complementary pairs in a darlington configuration) for the power amp, because the power amp needs to source a lot of current to low impedance loads, while the op amp is usually used as a voltage amp

 

[ronsimpson]

I suspect that's only on very old trucks

Double clutching is for tractors. It is typical on old tractors to come to a stop to change gears. There fore old tractors do not have synchronization parts. My old (40 years old) truck does not have problems. (10 forward gears and 2 reverse) If the transmission is worn out then double clutching, mostly in low gears, is a problem. My new truck is automatic.

 

[Nigel Goodwin]

Double clutching is for tractors. It is typical on old tractors to come to a stop to change gears. There fore old tractors do not have synchronization parts. My old (40 years old) truck does not have problems. (10 forward gears and 2 reverse) If the transmission is worn out then double clutching, mostly in low gears, is a problem. My new truck is automatic.

None of the tractors I've ever driven (none of them modern, or at all recent) 'required' double-declutching (though it helped), but certainly old trucks did - it was a big thing about becoming a truck driver back in the past.

Old motorbikes didn't have syncromesh gears either, never a problem on bikes.

 

[e44-72]

Thank you for the replies

 

[JMW]

An Op Amp amplifies Ops a power amp, amplifies power

 

[KeepItSimpleStupid]

Nigel:
This was an 18 wheel Tractor-trailer that I had to double clutch with air brakes. What initially confused me though was the clutch and the accelerator were hinged in the same manner, so the first tie I stopped wasn't very graceful. The trailer was fully loaded with paper products, so it was a little heavy.