Electronics > Beginners

Low Impedance Amplifier Suggestions

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darthhideous:
Hi all,

I'm looking for an amplifier capable of driving a 2 \$\Omega\$ (preferable) or 4 \$\Omega\$ (predominantly resistive with small XL) load with a minimum output power of ~100W. The required bandwidth is 50Hz - 200kHz. I'm not after a perfectly flat response across the band however at least 50W output is required at 200kHz. Operation would not be continuous with an estimated min duty cycle of 1 min on, 3 min off. Does anyone have suggestions for an off the shelf solution or alternatively power op-amps that could do this? I've had a look at the OPA549/OPA541 but they look dicey around 200kHz. I tried two LM3886s in parallel and they worked okay but hit their limit at around 200kHz.

Thanks!

David Hess:
What kind of distortion levels are acceptable?

Let's see; 100 watts into 2 ohms is 3.5 amps 7 volts so 7 amps 14 volts peak for sine waves.  What you are describing is essentially a super class-AB audio amplifier.  If you do not want to go the discrete route, then a part like the Apex MP111 is more than suitable if driven by a high level signal.  Another alternative would be something like several 7-lead TO-220 LT1210s in parallel.

I would probably try a variation of the first circuit included below using fast D44/D45 output transistors but that is just me.  My own old but similar discrete audio amplifier design had a bandwidth above 500kHz using much slower output transistors.

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