Dual-precision analog memory cell and array

1. A memory cell, comprising:

a non-volatile memory element having an input terminal and at least one output terminal; and

a volatile memory element having a plurality of input terminals and an output terminal, wherein the output terminal of the volatile memory element is coupled to the input terminal of the non-volatile memory element, and wherein the volatile memory element comprises:

a first transistor coupled between a first supply and a common node, and

a second transistor coupled between a second supply and the common node;

wherein the common node is coupled to the output terminal of the volatile memory element; and

wherein gates of the first and second transistors are coupled to respective ones of the plurality of input terminals of the volatile memory element.

2. The memory cell of claim 1 , wherein:

the first transistor is a P-type metal-oxide-semiconductor (PMOS) transistor; and

the second transistor is an N-type metal-oxide-semiconductor (NMOS) transistor.

3. The memory cell of claim 1 , wherein:

the non-volatile memory element comprises a floating-gate transistor, wherein a gate of the floating-gate transistor is coupled to the input terminal of the non-volatile memory element, and wherein a source and a drain of the floating-gate transistor are coupled to respective ones of the at least one output terminal of the non-volatile memory element.

4. The memory cell of claim 1 , wherein:

the non-volatile memory element comprises a ferro-electric transistor, wherein the ferro-electric transistor comprises a third transistor and a ferroelectric capacitor, wherein the ferroelectric capacitor is coupled between a gate of the third transistor and the input terminal of the non-volatile memory element, and wherein a source and a drain of the third transistor are coupled to respective ones of the at least one output terminal of the non-volatile memory element.

5. The memory cell of claim 1 , wherein the non-volatile memory element further comprises:

a third transistor coupled between the gate of the first transistor and a first word line, wherein a gate of the third transistor is coupled to a first bit line; and

a fourth transistor coupled between the gate of the second transistor and a second word line, wherein a gate of the fourth transistor is coupled to a second bit line.

6. The memory cell of claim 1 , wherein the non-volatile memory element further comprises:

a third transistor coupled between a source of the first transistor and the first supply, wherein a gate of the third transistor is coupled to a first word line, and wherein the gate of the first transistor is coupled to a first bit line; and

a fourth transistor coupled between a drain of the second transistor and a second supply, wherein a gate of the fourth transistor is coupled to a second word line, and wherein the gate of the second transistor is coupled to a second bit line.

7. The memory cell of claim 1 , wherein:

the first transistor is a first split-gate transistor having a first gate and a second gate, wherein the first gate is coupled to a first word line, and wherein the second gate is coupled to a first bit line; and

the second transistor is a second split-gate transistor having a third gate and a fourth gate, wherein the third gate is coupled to a second word line, and wherein the fourth gate is coupled to a second bit line.

8. A memory array, comprising:

an array of memory cells, wherein each memory cell comprises:

a non-volatile memory element having an input terminal and at least one output terminal; and

a volatile memory element having a plurality of input terminals and an output terminal, wherein the output terminal of the volatile memory element is coupled to the input terminal of the non-volatile memory element, and wherein the volatile memory element comprises:

a first transistor coupled between a first supply and a common node; and

a second transistor coupled between a second supply and the common node;

wherein the common node is coupled to the output terminal of the volatile memory element; and

wherein gates of the first and second transistors are coupled to respective ones of the plurality of input terminals of the volatile memory element.

9. The memory array of claim 8 , wherein:

the first transistor is a P-type metal-oxide-semiconductor (PMOS) transistor; and

the second transistor is an N-type metal-oxide-semiconductor (NMOS) transistor.

10. The memory array of claim 8 , wherein:

the non-volatile memory element comprises a floating-gate transistor, wherein a gate of the floating-gate transistor is coupled to the input terminal of the non-volatile memory element, and wherein a source and a drain of the floating-gate transistor are coupled to respective ones of the at least one output terminal of the non-volatile memory element.

11. The memory array of claim 8 , wherein:

the non-volatile memory element comprises a ferro-electric transistor, wherein the ferro-electric transistor comprises a third transistor and a ferroelectric capacitor, wherein the ferroelectric capacitor is coupled between a gate of the third transistor and the input terminal of the non-volatile memory element, and wherein a source and a drain of the third transistor are coupled to respective ones of the at least one output terminal of the non-volatile memory element.

12. The memory array of claim 8 , further comprising:

a control circuit configured to apply a first voltage pulse to the gate of the first transistor, and to apply a second voltage pulse to the gate of the second transistor;

wherein a charge at the common node increases by a fixed amount responsive to the first voltage pulse; and

wherein the charge at the common node decreases by the fixed amount responsive to the second voltage pulse.

13. The memory array of claim 12 , wherein the control circuit is further configured to modify a value stored in the non-volatile memory element according to a level of the charge at the common node.

14. A neural network, comprising:

an array of memory cells, wherein each memory cell comprises:

a non-volatile memory element having an input terminal and at least one output terminal; and

a volatile memory element having a plurality of input terminals and an output terminal, wherein the output terminal of the volatile memory element is coupled to the input terminal of the non-volatile memory element, and wherein the volatile memory element comprises:

a first transistor coupled between a first supply and a common node; and

a second transistor coupled between a second supply and the common node;

wherein the common node is coupled to the output terminal of the volatile memory element; and

wherein gates of the first and second transistors are coupled to respective ones of the plurality of input terminals of the volatile memory element.

15. The neural network of claim 14 , wherein:

the first transistor is a P-type metal-oxide-semiconductor (PMOS) transistor; and

the second transistor is an N-type metal-oxide-semiconductor (NMOS) transistor.

16. The neural network of claim 14 , further comprising:

a control circuit configured to apply a first voltage pulse to the gate of the first transistor, and to apply a second voltage pulse to the gate of the second transistor, during a training phase of the neural network;

wherein a charge at the common node increases by a fixed amount responsive to the first voltage pulse; and

wherein the charge at the common node decreases by the fixed amount responsive to the second voltage pulse.

17. The neural network of claim 16 , wherein the control circuit is further configured to modify a value stored in the non-volatile memory element according to a level of the charge at the common node during an update phase of the neural network.

18. The neural network of claim 17 , wherein the control circuit is further configured to read the value stored in the non-volatile memory element during an inference phase of the neural network.