AC-couple analog signals without a dc bias source

摘要

A conventional ac-coupling circuit in a single-supply system comprises a series capacitor and a shunt resistor to ground. Unfortunately, the negative peaks of the input signal can exceed the - 0.3V input operating-range limits 4f an ADG, such as the LTG1402 serial 12-bit sampling ADG. To avoid going below ground, the circuit must return the shunt input resistor to a midsupply voltage source. This problem is classic with all single-supply ADGs. You can use fully differential analog inputs, such as those of the LTG1402 2.2M-sample/sec, 12-bit, serial ADC, to ac-couple an analog signal without this midsupply bias voltage.