Download Differential-to-single-ended converter

Differential-to-single-ended converter
Hooman Hashemi,
National Semiconductor Corp,
Santa Clara, CA
The circuit in Figure 1 addresses applications in which you need to convert a
differential-current output to a single-ended voltage. Several analog modules, such as
the MC1495 multiplier and the LM1596 modulator/demodulator, provide differentialcurrent outputs. You can adjust R5 to adjust the voltage gain over the range of 5 to 201
to accommodate your application. The LM7121 op amp has a 2.5-GHz gain-bandwidth
product at a gain of 190. Because the LM7121 has unlimited capacitive driving
capability, you need not provide buffers for load isolation.
With >13-MHz bandwidth at a gain of 190 and 25V p-p output-swing capability (35
MHz and 4V p-p with a gain of 5), you can use the circuit for baseband video and audio
applications. The output slew rate is >700Vµsec, which allows for a full-power
bandwidth in excess of 8 MHz. You can trim the offset with R14; the input-offset
temperature coefficient is 30 µV/°C over the -40 to +85°C industrial temperature range.
You can adjust the R3 loop-gain trimmer to set the step response (that is, the damping
factor) of the amplifier for different gain settings. (DI #1842)