# operational amplifier?

i have a question regarding operational amplifier , here it goes,

is there any way to design such an opamp that takes

sin of its input ?

i.e Vo = Sin(vin)

if yes then please refer me to the circuit and explanation

Relevance
• Steven
Lv 7
8 years ago

Not exactly no. But older function generators used to take a triangular wave and soft clip it with a pair of diodes, or diode-resistor network, to produce a sine like wave. This never produced very good results and of course, only from -90° to +90°. Analog methods to produce a pure sine require a hi-Q filter so they are very slow to stabilize. Digital methods (DDS) work so much better.

http://en.wikipedia.org/wiki/Direct_digital_synthe...

http://www.analog.com/en/rfif-components/direct-di...

• 8 years ago

To get a sine output, you need to decide what range of angles you will accept--the sine wave keeps on repeating forever. For instance, you could represent 0 to pi/2 (0 to 90 degrees) with an input voltage of 0 to 10 volts. You could then have several feedback resistors in parallel, with each going through a zener diode. The zeners would be different voltages, all less than 10 volts. It's probably easier with a microprocessor, unless you need high speed. Also, with the micro, you can use any value for the angle and convert it to a value where your formula is accurate, say between 0 and 90 degrees, and then use the sine of the supplementary angle, or change the sign. There are several approximations for sine or cosine that are very close with just 3 or 4 terms. You would probably lose more accuracy in the A to D and D to A converters, anyway.

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• 8 years ago

No, but we usually approximate it with a logarithmic amplifier: this is sometimes used to shape a triangular wave into a sine wave. The results can actually be quite good. Have a read of this http://my.ece.ucsb.edu/bobsclass/2C/tutorials/App%... which deals mostly with oscillators to produce sine waves, but there are some logarithmic wave shaping circuits in there too, which are used to generate a sine wave from a triangle wave i.e. to aproximate Vo = sin(Vin)

• 8 years ago

No. There is no opamp circuit that can do it.

However, if the requirement is to implement a very close approximation of the sine function with a delay of a few milliseconds using any means possible, then an digital signal processor (DSP) can do it. You would probably program the DSP with an approximation of the Maclaren series for sin(x).