Flexible low noise, high linearity, high frequency, low power, fully differential mixer and class AB post-mixer amplifier system for SDR applications
A post-mixer amplifier device which receives and processes signals for use in a software-defined radio integrated circuit is provided. The post-mixer amplifier device includes but is not limited to a voltage amplifier having first and second inputs and a first output, a positive signal output connected with the first output of the voltage amplifier, and a positive signal input connected with a first bipolar junction transistor along a first pathway. The first bipolar junction transistor includes but is not limited to a first collector connected with a the first input of the voltage amplifier and a first emitter connected with an second output of the push-pull unity gain follower and forming a first current feedback pathway. The first bipolar junction transistor is driven with a passive resistive load.
1. A post-mixer amplifier device which receives and processes signals for use in a radio integrated circuit comprising:
a voltage amplifier having first and second inputs and a first output;
a push-pull unity gain follower having a third input and a second output, wherein the third input is connected with the first output of the voltage amplifier;
a positive signal output connected with the second output of the push-pull unity gain follower;
a positive signal input connected with a first switch, wherein the first switch is selectable between a first pathway and a second pathway;
a first bipolar junction transistor coupled to the positive signal input via the first switch along the first pathway, the first bipolar junction transistor having a first collector connected with the first input of the voltage amplifier and a first emitter coupled to the second output of the push-pull unity gain follower via a first resistance and forming a first current feedback pathway; and
a second bipolar junction transistor coupled to the positive signal input via the first switch along the second pathway, the second bipolar junction transistor having a second collector connected with the first input of the voltage amplifier and a second emitter coupled to the second output of the push-pull unity gain follower via a second resistance and forming a second current feedback pathway;
wherein the first and second bipolar junction transistors each drive passive resistive loads, coupled to the second output of the push-pull unity gain follower and the positive signal output, at their respective emitters, the passive resistive loads comprising the first and the second resistances, respective.
2. The device of claim 1 , wherein the first resistance comprises first resistor connected at a first end with the first emitter and at a second end with the second output of the push-pull unity gain follower and the second resistance comprises the first resistor in series with a second resistor connected at a first end with the second emitter and at a second end with the first end of the first resistor.
3. The device of claim 2 , wherein a gain of the post-mixer amplifier device may be varied by switching from the first pathway to the second pathway via the first switch.
4. The device of claim 1 , wherein the post-mixer amplifier device includes additional transistors, and first and second bipolar junction transistors have lower noise components than all other additional transistors in the post-mixer amplifier device.
5. The device of claim 1 , wherein the voltage amplifier is a voltage-mode operational amplifier.
6. The device of claim 1 , wherein the push-pull unity gain follower is a class AB voltage follower.
7. The device of claim 1 , wherein the first and second bipolar junction transistors include emitters that each have different gain setting resistance as a function of the first and second resistances such that a ratio that sets a closed-loop gain of the overall post-mixer amplifier device is different based on which one of the first and second bipolar junction transistors is selected via the first switch.
8. A post-mixer amplifier device which receives and processes signals for use in a radio integrated circuit comprising:
a voltage amplifier having first and second inputs and a first output;
a push-pull unity gain follower having a third input and a second output, wherein the third input is connected with the first output of the voltage amplifier;
a positive signal output connected with the second output of the push-pull unity gain follower;
a positive signal input; and
a first bipolar junction transistor coupled to the positive signal input and having a first collector connected with the first input of the voltage amplifier and a first emitter coupled to the second output of the push-pull unity gain follower via a first resistance and forming a first current feedback pathway;
wherein the first bipolar junction transistor drives a passive resistive load, coupled to the second output of the push-pull unity gain follower and the positive signal output, at its emitter, the passive resistive load comprising the first resistance.
9. The device of claim 8 , wherein the first resistance comprises a resistor connected at a first end with the first emitter and at a second end with the second output of the push-pull unity gain follower.
10. The device of claim 8 , wherein the post-mixer amplifier device includes additional transistors, and the first bipolar junction transistor has lower noise components than all other additional transistors in the post-mixer amplifier device.
11. The device of claim 8 , wherein the voltage amplifier is a voltage-mode operational amplifier.
12. A radio integrated circuit comprising:
a passive mixer outputting positive and negative signals;
a post-mixer amplifier which receives and processes the positive and negative signals, wherein the post-mixer amplifier includes:
a voltage amplifier having first and second inputs and a first output;
a push-pull unity gain follower having a third input and a second output, wherein the third input is connected with the first output of the voltage amplifier;
a positive signal output connected with the second output of the push-pull unity gain follower;
a positive signal input that receives the positive signal generated by the passive mixer; and
a first bipolar junction transistor coupled to the positive signal input and having a first collector connected with the first input of the voltage amplifier and a first emitter coupled to the second output of the push-pull unity gain follower via a first resistance and forming a first current feedback pathway;
wherein the first bipolar junction transistor drives a passive resistive load, coupled to the second output of the push-pull unity gain follower and the positive signal output, at its emitter, the passive resistive load comprising the first resistance.
13. The integrated circuit of claim 12 , wherein the fist resistance includes a resistor connected at a first end with the first emitter and at a second end with the second output of the push-pull unity gain follower.
14. The integrated circuit of claim 12 , wherein the positive signal input is connected with a first switch, and wherein the first switch is selectable between the first pathway, including the first bipolar junction transistor, and a second pathway, including a second bipolar junction transistor.
15. The integrated circuit of claim 14 , wherein a gain of the post-mixer amplifier device may be varied by switching from the first pathway to the second pathway.
16. The integrated circuit of claim 12 , wherein the post-mixer amplifier includes additional transistors, and the first bipolar junction transistor lower noise components than all other additional transistors in the post-mixer amplifier.