Abstract: A dual-port voltage control oscillator for use in a frequency synthesizer has first and second input ports and an output. The first port is coupled in a phase-locked-loop configuration for receiving input data and a reference frequency. The phase-locked-loop tunes the oscillator in response to a channel selection and trim parameter. The second port of the oscillator has a variable gain characteristic. A multiplier is coupled to the second port for multiplying the input data by a transfer function to alter the input data thereby compensating for the second port variable gain characteristic.

Abstract: A dual-port voltage control oscillator for use in a frequency synthesizer has first and second input ports and an output. The first port is coupled in a phase-locked-loop configuration for receiving input data and a reference frequency. The phase-locked-loop tunes the oscillator in response to a channel selection and trim parameter. The second port of the oscillator has a variable gain characteristic. A multiplier is coupled to the second port for multiplying the input data by a transfer function to alter the input data thereby compensating for the second port variable gain characteristic.

Abstract: A gain stage for providing an automatic phase shift is provided. In particular, the gain stage detects whether an oscillation signal appears at its inputs. If an oscillation signal is not detected, then the gain stage inverts output signals occurring at outputs of a first amplifier before being respectively applied to inputs of a second amplifier. This has the overall effect of implementing a 180.degree. phase shift of a signal appearing at the outputs of the gain stage with respect to a signal appearing at the inputs of the gain stage.

Abstract: An on-chip self-test circuit has been provided that allows for accurately testing a device such as prescaler at high frequencies. The on-chip self-test circuit includes a voltage controlled oscillator for providing high frequency signals to the device under test.The on-chip self-test circuit is rendered active only when one desires to test the device. Thus, when not testing, the on-chip self-test circuit is transparent to the device and consumes substantially zero power.