Continue to Site

Welcome to

Welcome to our site! is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Help needed with amplifier design.

Not open for further replies.


Junior Member level 1
Apr 5, 2009
Reaction score
Trophy points
Activity points
I am generating a sine wave using a micro-controller and resistive ladder,freq of 100Hz-800Khz. it is than shifted to 0v origin using level shifter circuit, and amplified to 5V peak to peak.
I need this 5Vpp signal to amplified to 70vpp-90Vpp, using a suitable voltage amplifier, do I use a single stage amplifier to do this or a 2 stage, like the first one amplifies to 30Vpp a filter stage in between and than a second stage to take it to 70vpp or 90vpp. What sort of amplifier should be used class A or Class AB.
dual supply voltage of +/-50V can be provided using a SMPS , the output voltage swing is needed more than the power [current]. the load is a 8Ohm coil.Any circuit or theory will help.
Please advise. Thank you.

Good audio power amplifiers are able to achieve the intended bandwidth, at least after adjusting the frequency compensation. Many examples have been posted a edaboard before. If low distortion isn't an objective, a more simple circuit may be sufficient. Class AB should be preferred in any case.

A "coil" can be expected rather as an inductive than resistive load, I think.

Best to use Inductive based two stage amplifier. First stage could be used as pre-amplifier for boosting voltage level and second stage with low gain and high current booster amplifier. An inductive based amplifier only helps to abrupt amplification of input signal.

Best to use Inductive based two stage amplifier.
Don't know what you exactly mean with "inductive based". The requirement is wideband operation 100Hz-800Khz.

The 100Hz to 800 Khz is the frequency generated using a controller, it's for an experiment I need to perform, so I need to generate frequency from100Hz to 800Khz. The load is a single turn copper coil, with a 8ohm resistance in series this can be changed for impedance matching, but right now ,I have being doing my experiment with 8 ohm resistor.

I need more voltage in the coil, that what I need to achieve to proceed further.
The sine way should be distortion free as it will be picked up by a matching receiver and compared to the generated wave later.
Any good amplifier circuit available will help.

90 V p-p ~ 32V rms / 8 = 4A X 32 = 128W!!!! You will need a very good FET Hi Fi amp that you are going to have to tweak to maintain its loop gain at 800KHz.

Frank , That's why I need help with theory of a good amplifier. And hence the choice of a Class AB amplifier for the experiment.Any help with design of the amplifier [class AB] over the frequency range would help.

Not open for further replies.

Part and Inventory Search

Welcome to