Regulator and temperature compensation bias circuit for linearized power amplifier
View Patent ↗An improved regulator circuit, temperature compensation bias circuit, and amplifier circuit are disclosed.
1. A temperature compensated bias circuit of a radio frequency transistor having a control terminal, a first current carrying terminal, and a second current carrying terminal, comprising:
an output providing a temperature compensated bias to a radio frequency transistor;
a first transistor having a control terminal, a first current carrying terminal receiving power from a first regulated voltage source, and a second current carrying terminal coupled to the output;
a second transistor having a control terminal coupled to the second current carrying terminal of the first transistor and the output, a first current carrying terminal receiving power from a second regulated voltage source, and a second current carrying terminal coupled to a ground; and
a diode at an intermediate position between the second regulated voltage source and the first current carrying terminal of the second transistor, the diode determining current through the first current carrying terminal of the second transistor, and the current through the first current carrying terminal of the second transistor determines a first voltage difference between the control terminal of the second transistor and the second current carrying terminal of the second transistor.
2. The circuit of claim 1 , wherein at least one of the first transistor and the second transistor is a bipolar junction transistor, such that the control terminal of the bipolar junction transistor is a base terminal, the first current carrying terminal of the bipolar junction transistor is a collector terminal, and the second current carrying terminal of the bipolar junction transistor is an emitter terminal.
3. The circuit of claim 1 , wherein at least one of the first transistor and the second transistor is an enhancement mode pseudomorphic high electron mobility transistor, and the control terminal of the enhancement mode pseudomorphic high electron mobility transistor is a gate terminal, the first current carrying terminal of the enhancement mode pseudomorphic high electron mobility transistor is a drain terminal, and the second current carrying terminal of the enhancement mode pseudomorphic high electron mobility transistor is a source terminal.
4. The circuit of claim 1 , wherein the first voltage difference determines a second voltage difference between a control terminal of the radio frequency transistor and the second current carrying terminal of the radio frequency transistor.
5. The circuit of claim 1 , wherein responsive to temperature variation, the current through the first current carrying terminal of the second transistor determined by the diode, but the first voltage difference of the second transistor changes with temperature variation.
6. The circuit of claim 1 , wherein responsive to temperature variation, the current through the first current carrying terminal of the second transistor determined by the diode, but the first voltage difference of the second transistor changes with temperature variation, such that the first voltage difference determines a temperature compensated voltage difference between a control terminal of the radio frequency transistor and the second current carrying terminal of the radio frequency transistor.
7. The circuit of claim 1 , wherein the second transistor has a floating voltage of a difference between the first and second current carrying terminals.
8. The circuit of claim 1 , wherein over a range of an output power of the radio frequency transistor, the first transistor has a current through the first current carrying terminal which increases with the output power of the radio frequency transistor, and the range of an output power of the radio frequency transistor includes an upper power range over a threshold power and a lower power range under the threshold power, such that a rate of increase of the current through the first current carrying terminal of the first transistor is less in the upper power range than in the lower power range, thereby at least partly compensating for nonlinearity of the radio frequency transistor in the upper power range.