Granted Patent B2

US 8,665,007 · App. 13/490,254 · Granted Mar 4, 2014

Abstract

Claims (13)

1. A clamp circuit for an RFID tag comprising:

a power supply node;

a dynamic clamp coupled between the power supply node and ground; and

an active clamp coupled between the power supply node and ground, wherein the combined action of the dynamic and active clamps moderate the behavior of the power supply node to fast rising RF inputs,

wherein the active clamp comprises a differential amplifier having a first input coupled to a resistor divider, a second input for receiving a reference voltage, and is coupled to a transistor for providing a clamped voltage (VDDR) from the power supply node.

2. The clamp circuit of claim 1 wherein the dynamic clamp comprises a capacitor divider circuit.

3. The clamp circuit of claim 2 wherein the dynamic clamp comprises a resistor coupled to the capacitor divider circuit.

4. The clamp circuit of claim 2 wherein the dynamic clamp comprises a transistor coupled to the capacitor divider circuit.

5. The clamp circuit of claim 4 wherein the transistor within the dynamic clamp comprises an N-channel transistor.

6. The clamp circuit of claim 1 wherein the differential amplifier comprises an operational amplifier.

7. The clamp circuit of claim 1 wherein the differential amplifier comprises a comparator.

8. The clamp circuit of claim 1 wherein the transistor comprises a P-channel transistor.

9. The clamp circuit of claim 8 wherein the clamped VDDR voltage is provided at a source of the P-channel transistor.

Assignments (6)