Integrated RF front end with stacked transistor switch
View Patent ↗A monolithic integrated circuit (IC), and method of manufacturing same, that includes all RF front end or transceiver elements for a portable communication device, including a power amplifier (PA), a matching, coupling and filtering network, and an antenna switch to couple the conditioned PA signal to an antenna. An output signal sensor senses at least a voltage amplitude of the signal switched by the antenna switch, and signals a PA control circuit to limit PA output power in response to excessive values of sensed output. Stacks of multiple FETs in series to operate as a switching device may be used for implementation of the RF front end, and the method and apparatus of such stacks are claimed as subcombinations. An iClass PA architecture is described that dissipatively terminates unwanted harmonics of the PA output signal. A preferred embodiment of the RF transceiver IC includes two distinct PA circuits, two distinct receive signal amplifier circuits, and a four-way antenna switch to selectably couple a single antenna connection to any one of the four circuits.
1. An integrated RF Power Amplifier (PA) circuit, comprising:
a) an input node to accept an input signal with respect to a reference voltage Vref, coupled to a gate G 1 of a first insulated-gate FET M 1 ;
b) a plurality of additional insulated-gate FETs M 2 to Mn having a same polarity as M 1 and coupled in series with M 1 to form a control circuit configured to control conduction between the reference voltage and an output drive node, wherein FETs M 2 to Mn are each enslaved to M 1 ;
c) an output coupling capacitor coupling the output drive node to an output load node; and
d) an output power control input node coupled to a power controlling insulated-gate FET that is coupled in series connection with M 1 .
2. The integrated circuit of claim 1 , wherein the power controlling FET is disposed between the reference voltage and a power supply voltage external to the PA.
3. The integrated circuit of claim 1 , wherein the power controlling FET is one of the FETs M 2 to Mn.
4. The integrated circuit of claim 1 , further comprising a low-pass filter disposed in series with the output coupling capacitor between the output drive node and the output load node.
5. An integrated RF Power Amplifier (PA) circuit, comprising:
a) an input node to accept an input signal with respect to a reference voltage Vref, coupled to a gate G 1 of a first insulated-gate FET M 1 ;
b) a plurality of additional insulated-gate FETs M 2 to Mn having corresponding gates G 2 to Gn and a same polarity as M 1 and coupled in series with M 1 to form a control circuit configured to control conduction between the reference voltage and an output drive node, wherein FETs M 2 to Mn are each enslaved to M 1 ;
c) an output coupling capacitor coupling the output drive node to an output load node; and
d) a corresponding predominantly capacitive element connected directly between each gate, G 2 to Gn, and Vref.
6. The integrated circuit of claim 5 , further comprising (e) an output power control input node coupled to a power controlling insulated-gate FET that is coupled in series connection with M 1 .
7. The integrated circuit of claim 6 , wherein the power controlling FET is disposed between the reference voltage and a power supply voltage external to the PA.
8. The integrated circuit of claim 6 , wherein the power controlling FET is one of the FETs M 2 to Mn.
9. The integrated circuit of claim 5 , further comprising a low-pass filter disposed in series with the output coupling capacitor between the output drive node and the output load node.