Driver circuit employing high-speed tri-state for automatic test equipment

A driver circuit, comprising:

• a driver input for receiving an input signal;
• a driver output for producing an output signal;
• a first amplifier having a plurality of inputs, one of said inputs being coupled to the driver input, and an output coupled to the driver output and configured for substantially sourcing current only;
• a second amplifier having a plurality of inputs, one of said inputs being coupled to the driver input, and an output coupled to the driver output and configured for substantially sinking current only;
• and
• means for disabling the driver circuit, having an input for receiving a drive disable signal, a first output coupled to at least one of the plurality of inputs of the first amplifier, and a second output coupled to at least one of the plurality of inputs of the second amplifier,
• wherein the means for disabling the driver circuit includes means, responsive to the activation of a drive disable signal, for driving the outputs of the first and second amplifiers so that the output of the first amplifier is lower than the output of the second amplifier.

A method of generating an output signal from an input signal for stimulating a device under test (DUT) in an automatic test system, comprising:

• generating a first voltage proportional to the input signal, from a first circuit that can substantially source current only;
• generating a second voltage proportional to the input signal, from a second circuit that can substantially sink current only;
• combining the first and second voltages via at least one impedance to produce the output signal, wherein the first voltage is normally greater than the second voltage;
• and
• driving, in response to the assertion of a drive disable signal, at least one of the first and second circuits to cause the second voltage to exceed the first voltage, thereby causing the output signal to assume a high impedance state.

A circuit for generating a signal for testing a device, comprising:

• an input for receiving an input signal;
• an output for producing an output signal;
• a plurality of driver circuits, each including:
• a driver input;
• a driver output;
• a first amplifier having an input coupled to the driver input and an output coupled to the driver output and arranged for substantially sourcing current only;
• a second amplifier having an input coupled to the driver input and an output coupled to the driver output and arranged for substantially sinking current only;
• and
• a disable circuit having an input for receiving at least one drive disable signal and at least one output coupled to the first and second amplifiers,
• wherein the disable circuit is constructed and arranged to drive at least one of the first and second amplifiers so that the output of the first amplifier is lower than the output of the second amplifier;
• and
• a plurality of output impedances, each having a first node coupled to a different driver output of the plurality of driver circuits and a second node coupled to the second node of each of the other of the plurality of output impedances.

A driver circuit, comprising:

• a driver input for receiving an input signal;
• a driver output for producing an output signal;
• a first amplifier having an input coupled to the driver input and an output coupled to the driver output and arranged for substantially sourcing current only;
• and
• a second amplifier having an input coupled to the driver input and an output coupled to the driver output and arranged for substantially sinking current only,
• wherein the driver circuit is constructed and arranged to drive, responsive to the assertion of at least one drive disable signal, at least one of the first and second amplifiers so that the output of the first amplifier is lower than the output of the second amplifier.