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Convert 150 Ohm differential impedance to 100 Ohm differential impedance

photelectron

Oct 2, 2018
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Oct 2, 2018
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Hi

I am new to circuit design. I have to interface the MAXIM TIA MAX 40658 which has 150 Ohm differential impedance, to an ADC which as an 100 Ohm differential impedance input. The important aspect is the bandwidth requirement is from 50 KHz to 300 MHz. The ADC requires a common mode input voltage of 1.25V. Can anybody advise how to implement this.

Many Thanks
 

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hevans1944

Hop - AC8NS
Jun 21, 2012
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Jun 21, 2012
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Where is the datasheet for the ADC? This looks like a pretty ambitious project for anyone "new to circuit design." What is the application?

The MAXIM product was designed for use with a reverse-biased high-speed photo-diode, operating in transconductance mode (current-to-voltage converter), typically in a pulsed LIDAR application to measure "time-of-flight" and hence calculate range from the point of laser pulse emission to photo-diode detection of the reflected light pulse.

LIDAR is basically an analog application with digital timing measurement and digital calculation and correction of the indicated range affected by environmental factors such as air density, temperature, and so on. MAXIM recommends using their product as a bare die, and wire-bonding the selected photo-diode to the die, to minimize parasitic capacitance at the diode connection to the transimpedance amplifier. This is necessary to preserve bandwidth, which affects range resolution.

Of course if your application doesn't involve LIDAR, perhaps being more communication oriented with modulated light carrying data or other information, then other considerations will apply. No one here can help you without more information of what you are trying to DO. Words are cheap. Use plenty of them to fully describe your problem, not your imagined solution.
 
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