| 摘要 |
An isolation amplifier including a full-wave modulator which applies to the primary winding of an isolation transformer an attenuated version of the input signal, to reduce the flux density in the transformer without the need for a complicated flux-nulling feedback arrangement. This is a wide-band modulator with means for protection against the adverse effects of thermal drift in the attenuator. Two or more resistors create a resistive divider across the signal and ground terminals of the isolator's input port. A tap on the resistive divider is connected to the input of a first buffer amplifier whose output is connected in series with a capacitor to one lead of the primary winding of the transformer. The signal input is supplied to one throw of an SPDT analog voltage switch, the other throw of which is connected to ground. The pole of the switch is connected to the input of a second buffer amplifier and the output of that buffer is connected to the other lead of the transformer primary. A carrier signal from a carrier source controls the opening and closing of this switch to "chop" the input signal and provide a modulated input to the transformer. A synchronous demodulator connected to the transformer secondary demodulates the chopped input signal.
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