Method of and apparatus for providing a high speed video switch

A method of switching between a plurality of input video signals and generating an output video signal representative of one of the plurality of input video signals comprising the steps of:

• a. receiving a plurality of input video signals;
• b. receiving one or more control signals specifying an appropriate one of the plurality of input video signals to be output;
• c. providing a current-mode control signal from a single current source in response to the one or more control signals;
• and
• d. generating an output video signal representative of an appropriate one of the plurality of input video signals as controlled by the current-mode control signal.

A video switching circuit for generating an output signal representative of one of a plurality of input video signals comprising:

• a. a plurality of input receiving circuits each configured for receiving one of the plurality of input video signals;
• b. a control signal receiving circuit configured for receiving one or more control signals, wherein the control signals specify which one of the plurality of input video signals are to be output;
• c. a current source for generating a predetermined current;
• d. a current mode switching circuit coupled to the control signal receiving circuit, to each of the plurality of input receiving circuits and to receive the predetermined current, wherein the current mode switching circuit routes the predetermined current to a selected one of the plurality of input receiving circuits for generating an output signal representative of one of the plurality of input video signals as controlled by the one or more control signals, wherein the current mode switching circuit includes an isolation circuit for each of the plurality of input video signals for isolating all of the plurality of input video signals from the output signal except for the one of the plurality of input video signals which is represented by the output signal.

A video switching circuit for generating an output signal representative of a predetermined one of a first input video signal and a second input video signal, the video switching circuit comprising:

• a. a first receiving circuit configured for receiving the first input video signal;
• b. a second receiving circuit configured for receiving the second input video signal;
• c. a current mode switching circuit configured for receiving one or more control signals and coupled to the first and second receiving circuits for generating an output signal representative of a predetermined one of the first and second input video signals;
• d. a first clamping circuit coupled to the first receiving circuit and to the current mode switching circuit for clamping a first blank level of the first input video signal to a predetermined level, wherein the current mode switching circuit further comprises a first isolation circuit coupled to the first clamping circuit and to the current mode switching circuit for isolating the first input video signal from the output signal when the output signal represents the second input video signal;
• and
• e. a second clamping circuit coupled to the second receiving circuit and to the current mode switching circuit for clamping a second blank level of the second input video signal to the predetermined level.

A video switching circuit for generating an output signal representative of a predetermined one of a first input video signal and a second input video signal, the video switching circuit comprising:

• a. a first receiving circuit configured for receiving the first input video signal;
• b. a second receiving circuit configured for receiving the second input video signal;
• c. a current mode switching circuit configured for receiving one or more control signals and coupled to the first and second receiving circuits for generating an output signal representative of a predetermined one of the first and second input video signals;
• d. a first clamping circuit coupled to the first receiving circuit and to the current mode switching circuit for clamping a first blank level of the first input video signal to a predetermined level, wherein the current mode switching circuit further comprises a first isolation circuit coupled to the first clamping circuit and to the current mode switching circuit for isolating the first input video signal from the output signal when the output signal represents the second input video signal;
• and
• e. a second clamping circuit coupled to the second receiving circuit and to the current mode switching circuit for clamping a second blank level of the second input video signal to the predetermined level, wherein the current mode switching circuit further comprises a second isolation circuit coupled to the second clamping circuit and to the current mode switching circuit for isolating the second input video signal from the output signal when the output signal represents the second input video signal.