High output 600 Ohm line driver


Posted on Jul 13, 2012

The circuit has a `floating` output, i.e., it behaves like an isolated transformer winding, with the output amplitude remaining unchanged whether the center or either end of the load is grounded. This is achieved by making Z-out, common mode, infinite. The circuit consists of two current-sources in push-pull. Since each has infinite output Z, the common mode output impedance is also infinite. Connecting a resistor between the non-inverting terminals of the op amps reduces the differential Z-out without affecting the Z-common-mode. Since the output is floating, if the load is also floating there is no output ground reference, which results in malfunction.


High output 600 Ohm line driver
Click here to download the full size of the above Circuit.

This can be corrected by reducing the common-mode slightly. R7 fulfills this function. All resistors should be of close tolerance to give a good balance. The line driver provides +24 dB from ± 12 V or +16 dB from ±6 V supplies.




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