need L290 substitute

Hello, all,

Why is it whenever I find the PERFECT chip for something, it turns out to be discontinued? I found the L290 from SGS-Thompson, an old part that converts quadrature encoder signals to bipolar voltage proportinal to frequency. It looks like it could be real difficult to get this part, except from the vultures. It is basically a double F-V converter, so it produces a voltage proportional to count rate, with the sign of the output indicating the direction the encoder is turning. I think I know how to do this with 2 F-V converters and some logic, but I can't get it below about 6 chips. Does anyone know of a replacement for the L290 or L290B that does the same quadrature to bipolar voltage conversion?

Just to prevent bad suggestions, you can't use one F-V and a sign inverter after it because of encoder dithering. The balanced approach will always see equal numbers of steps in + and - direction and cancel them out. The single scheme would produce a rapidly flickering non-zero voltage proportional to the dithering rate, which would drive a servo system crazy.

Thanks in advance for any helpful ideas!

Jon
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