Analog switch for transmitting high voltage signals without utilizing high voltage power supplies
Described herein are multiple designs for an improved analog switch for use in transmitting high voltage signals without using high voltage power supplies for the switch. The analog switches are able to pass and block input signals in the approximate range of −100V to +100V. The use of translinear loops and a bootstrap configuration results in a constant on-resistance of the symmetrical switches and matches the conductance of each analog switch to the transconductance of an NMOS transistor, which can be easily stabilized with a constant g m biasing scheme. In certain embodiments, a shunt termination (T-switch) configuration is used for better off-isolation, and each of the symmetrical switches has its own translinear loop and thus flexibility of on-resistance and termination voltage.
1. An analog switch, comprising:
a first transistor comprising a first terminal, a second terminal, and a gate, wherein the first terminal is configured to receive a high voltage input signal and the gate receives a first voltage when a control signal is low and receives a second voltage when the control signal is high, wherein the magnitude of the first voltage and the magnitude of the second voltage are smaller than the magnitude of the high voltage input signal;
a second transistor comprising a first terminal, a second terminal, and a gate, wherein the first terminal of the second transistor is coupled directly or indirectly to the second terminal of the first transistor, the gate of the second transistor receives the first voltage when the control signal is low and receives the second voltage when the control signal is high, and the second terminal of the second transistor presents the high voltage input signal when the gate of the second transistor receives the first voltage and blocks the high voltage input signal when the gate of the second transistor receives the second voltage; and
a shunt circuit connected to a node between the first transistor and the second transistor, wherein the shunt circuit pulls the node to ground when the control signal is high, and wherein the shunt circuit is powered by the first voltage and the second voltage.
2. The analog switch of claim 1 , wherein the high voltage input signal ranges between +100 volts and −100 volts.
3. The analog switch of claim 1 , wherein the shunt circuit does not alter the voltage of the node between the first transistor and the second transistor when the when the control signal is low.
4. A medical ultrasound device, comprising:
a probe; and
a plurality of transducers, each transducer coupled to the probe through an analog switch;
wherein each analog switch comprises:
a first transistor comprising a first terminal, a second terminal, and a gate, wherein the first terminal is configured to receive a high voltage input signal and the gate receives a first voltage when a control signal is low and receives a second voltage when the control signal is high, wherein the magnitude of the first voltage and the magnitude of the second voltage are smaller than the magnitude of the high voltage input signal;
a second transistor comprising a first terminal, a second terminal, and a gate, wherein the first terminal of the second transistor is coupled directly or indirectly to the second terminal of the first transistor, the gate of the second transistor receives the first voltage when the control signal is low and receives the second voltage when the control signal is high and the second terminal of the second transistor presents the high voltage input signal when the gate of the second transistor receives the first voltage and blocks the high voltage input signal when the gate of the second transistor receives the second voltage; and
a shunt circuit connected to a node between the first transistor and the second transistor, wherein the shunt circuit pulls the node to ground when the control signal is high and wherein the shunt circuit is powered by the first voltage and the second voltage.
5. The medical ultrasound device of claim 4 , wherein the high voltage input signal ranges between +100 volts and −100 volts.