Circuit employing MOSFETs and corresponding method
View Patent ↗A MOSFET has a current conduction path between source and drain terminals. A gate terminal of the MOSFET receives an input signal to facilitate current conduction in the current conduction path as a result of a gate-to-source voltage reaching a threshold voltage. A body terminal of the MOSFET is coupled to body voltage control circuitry that is sensitive to the voltage at the gate terminal of the MOSFET. The body voltage control circuitry responds to a reduction in the voltage at the gate terminal of the MOSFET by increasing the body voltage of the MOSFET at the body terminal of the MOSFET. As a result, there is reduction in the threshold voltage. The circuit configuration is applicable to amplifier circuits, comparator circuits and current mirror circuits.
1. A circuit, comprising:
a first MOSFET having a current conduction path between a first source terminal and a first drain terminal, a first gate terminal configured to receive a first input signal and a first body terminal;
a second MOSFET having a current conduction path between a second source terminal and a second drain terminal, a second gate terminal configured to receive a second input signal and a second body terminal;
wherein said first and second MOSFETs are coupled with each other in a differential MOSFET pair and the first and second input signals are a differential input signal;
body voltage control circuitry, comprising:
a first body voltage control MOSFET having a gate terminal coupled to the first gate terminal of said first MOSFET and configured to receive the first input signal of the differential input signal, and a first source-drain current path;
a second body voltage control MOSFET having a gate terminal coupled to the second gate terminal of said second MOSFET and configured to receive the second input signal of the differential input signal and a second source-drain current path;
wherein the first and second source-drain current paths are coupled in series with each other between the first body terminal of the first MOSFET and a reference node.
2. The circuit of claim 1 , wherein the first and second source-drain current paths are coupled in series with each other between the second body terminal of the second MOSFET and the reference node.
3. The circuit of claim 2 , wherein the first and second body terminals are directly electrically connected.
4. The circuit of claim 1 , wherein the reference node is ground.
5. The circuit of claim 1 , wherein body terminals of the first and second body voltage control MOSFETs are directly electrically connected to the first body terminal of the first MOSFET.
6. The circuit of claim 1 , wherein body terminals of the first and second body voltage control MOSFETs are directly electrically connected to the second body terminal of the second MOSFET.
7. The circuit of claim 1 , wherein a polarity type of the first and second body voltage control MOSFETs is same as a polarity type of said first MOSFET.
8. The circuit of claim 1 , further comprising a current source configured to apply a bias current to the first body terminal of the first MOSFET.
9. The circuit of claim 1 , wherein the body voltage control circuitry is configured to respond to change of the differential input signal by changing a body voltage at the first body terminal of the first MOSFET in order to adjust a threshold voltage of the first MOSFET.
10. The circuit of claim 9 , wherein the adjustment of the threshold voltage is a reduction of the threshold voltage.
11. The circuit of claim 1 , wherein the body voltage control circuitry is configured to respond to change of the differential input signal by changing a body voltage at the second body terminal of the second MOSFET in order to adjust a threshold voltage of the second MOSFET.
12. The circuit of claim 11 , wherein the adjustment of the threshold voltage is a reduction of the threshold voltage.