Hybrid AC/DC-coupled channel for automatic test equipment

1. A channel for use in automatic test equipment and adapted for coupling to a device-under-test, the channel including:

a driver circuit;

a first AC-coupled signal path disposed at the output of the driver circuit and configured to propagate signal components at and above a predetermined frequency; and

a first DC-coupled signal path disposed at the output of the driver circuit in a parallel relationship with the first AC-coupled signal path and configured to propagate signal components from DC to the predetermined frequency.

2. A channel according to claim 1 and further including:

a user-programmable selector to establish either the AC-coupled signal path, or both the AC and DC-coupled signal paths in operation.

3. A channel according to claim 1 wherein:

the DC-coupled signal path includes a filter operative on the signal components from DC to the predetermined frequency according to a predefined transfer function, the transfer function preserving the phase and frequency of the signal components from DC to the predetermined frequency, and offsetting any DC voltage component by a predetermined amount.

4. A channel according to claim 1 and further including:

a comparator circuit;

a second AC-coupled signal path disposed at the comparator input and configured to propagate signal components at and above a predetermined frequency; and

a second DC-coupled signal path disposed at the comparator input in a parallel relationship with the second AC-coupled signal path and configured to propagate signal components from DC to the predetermined frequency.

5. A channel for use in automatic test equipment and adapted for coupling to a device-under-test, the channel including:

a comparator;

a second AC-coupled signal path disposed at the comparator input and configured to propagate signal components at and above a predetermined frequency; and

a second DC-coupled signal path disposed in parallel with the AC-coupled signal path and configured to propagate signal components from DC to the predetermined frequency.

6. A channel according to claim 5 and further including:

a user-programmable selector to establish either the AC-coupled signal path or both the AC and DC-coupled signal paths in operation.

7. A channel according to claim 5 wherein:

the second DC-coupled signal path includes a current injection circuit.

8. A channel for use in automatic test equipment and adapted for coupling to a device-under-test, the channel including:

means for driving a differential signal;

means for AC-coupling the means for driving a differential signal to the device-under-test; and

means for DC-coupling the means for driving a differential signal to the device-under-test.

9. A channel according to claim 8 and further including:

means for selecting for operation either the means for AC-coupling or both the means for AC-coupling and the means for DC-coupling.

10. A channel according to claim 8 wherein the means for DC-coupling includes:

a filter operative on the signal components from DC to the predetermined frequency according to a predefined transfer function, the transfer function preserving the phase and frequency of the signal components from DC to the predetermined frequency, and offsetting any DC voltage component by a predetermined amount.

11. A channel according to claim 8 and further including:

means for comparing a differential signal to a reference signal;

means for AC-coupling the means for comparing to the device-under-test; and

means for DC-coupling the means for comparing to the device-under-test.

12. A channel according to claim 8 wherein the means for DC-coupling includes:

means for injecting a current into the means for comparing.