Has anyone used the OPA445 as the "driver" in a power amp? What voltages did you feed it? The datasheet says abs. max 50V each rail, and I was thnking of feeding it 48V each rail so as to make a 200W/4R audio amp!
48V rails are too high, 45V is the max recommended. When you look into what additional circuitry you need (e.g. bias and drivers), it is just as easy and simple and actually cheaper to make a discrete amp.
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OPA445 also has only 2MHz GBP. Among high voltage integrated control devices quite a bit more loop gain is available from the LME49810 and LME49830.
Just saw this and I have also looked into using the OPA445 as part of an amp build. Take a look at the SSA35, SSA120 amps at by-rutgers dot nl which are also referenced in this post
Power Amplifier with Small Signal OP-Amp in the Front-End - Overview wanted
Power Amplifier with Small Signal OP-Amp in the Front-End - Overview wanted
I find OPA453 has better bandwidth in circuit.
OPA453 can take +/- 40 Volt supply.
But as I said, you get better frequency with OPA453.
OPA453 can deliver 50mA and it is one TO-220 capsule.
http://www.ti.com/lit/ds/symlink/opa452.pdf
You have a DC gain of 18 as well AC gain of 18.
Most power amps use DC gain of 1 to keep them more stable during temperature change.
I would have used an AC coupling capacitor and resistor to ground on input to set GND level.
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Yes. The amp output offset will be the opamp output offset times 18. I don't think it will drift a lot, but could be appreciable, max spec is 3mV.
And yes, cap in series with that 1k at the input would fix it.
Jan
And yes, cap in series with that 1k at the input would fix it.
Jan
I would think that a single pair of outputs would work at that voltage, unless I’m missing something?
Nice simple circuit!
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