Input Coupling

The signal applied to the CH 1 OR X input connector can be ac-coupled, dc-coupled, or internally disconnected from the input of the High-Z Input Attenuator circuit.

Signals applied to the CH 1 input connector are routed through resistor R101 to Input Coupling switch S101. When S101 is set for dc coupling, the CH 1 signal is applied directly to the input of the High-Z Attenuator stage. When ac-coupled, the input signal passes through R100 and dc-blocking capacitor C102. The blocking capacitor prevents the dc component of the input signal from being applied to the Attenuator circuit. When S101 is set to GND, the direct signal path is opened and the input of the attenuator is connected to ground. This provides a ground reference without the need to disconnect the applied signal from the input connector. The coupling capacitor is allowed to precharge through R102, a high-resistance component, which is connected across Input Coupling switch S101 in the GND position.

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