Apparatus and methods for overload protection of low noise amplifiers
Apparatus and methods for overload protection of low noise amplifiers (LNAs) are provided herein. In certain configurations, an LNA system includes an input switch having an analog control input that controls an impedance of the input switch, an LNA that amplifies a radio frequency (RF) input signal received from the input switch, and an overload protection circuit that provides feedback to the input switch's analog control input based on detecting a signal level of the LNA. The overload protection circuit detects whether or not the LNA is overloaded. Additionally, when the overload protection circuit detects an overload condition, the overload protection circuit provides feedback to the analog control input of the switch to increase the impedance of the switch and reduce the magnitude of the RF input signal received by the LNA.
1. A low noise amplifier system comprising:
an input switch having an analog control input operable to control an impedance of the input switch;
a low noise amplifier configured to provide amplification to a radio frequency input signal received from the input switch;
an overload protection circuit configured to provide feedback to the analog control input of the input switch based on a detected signal level of the low noise amplifier; and
a limiter enable circuit configured to selectively connect an output of the overload protection circuit to the analog control input based on a switch enable signal, the limiter enable circuit operable to disconnect the output of the overload protection circuit from the analog control input and turn off the input switch when the switch enable signal is in a disabled state.
2. The low noise amplifier system of claim 1 wherein the overload protection circuit is configured to increase the impedance of the input switch to reduce a magnitude of the radio frequency input signal in response to determining that the detected signal level indicates an overload condition.
3. The low noise amplifier system of claim 1 wherein the limiter enable circuit is further configured to selectively connect the output of the overload protection circuit to the analog control input based on a state of a limiter enable signal.
4. The low noise amplifier system of claim 1 wherein the overload protection circuit includes a detector configured to generate a detection signal indicating the detected signal level of the low noise amplifier, and an error amplifier configured to provide feedback to the analog control input based on amplifying a difference between the detection signal and a reference signal.
5. A low noise amplifier system comprising:
an input switch having an analog control input operable to control an impedance of the input switch;
a low noise amplifier configured to provide amplification to a radio frequency input signal received from the input switch; and
an overload protection circuit configured to provide feedback to the analog control input of the input switch based on a detected signal level of the low noise amplifier, the overload protection circuit including a detector configured to generate a detection signal indicating the detected signal level of the low noise amplifier, and an error amplifier configured to provide feedback to the analog control input based on amplifying a difference between the detection signal and a reference signal, the detector including a bipolar transistor configured to saturate in response to an overload condition of the low noise amplifier.
6. The low noise amplifier system of claim 5 wherein the detector further includes a capacitor configured to filter a current flowing through the bipolar transistor, the detector configured to generate the detection signal based on a voltage across the capacitor.
7. The low noise amplifier system of claim 1 wherein the detected signal level includes an output signal level of the low noise amplifier.
8. The low noise amplifier system of claim 1 wherein the detected signal level includes an internal signal level of the low noise amplifier.
9. A packaged front end module comprising:
a packaging substrate; and
an integrated circuit attached to the packaging substrate, the integrated circuit including an input switch having an analog control input operable to control an impedance of the input switch, a low noise amplifier configured to provide amplification to a radio frequency input signal received from a first throw of the input switch, an overload protection circuit configured to provide feedback to the analog control input of the input switch based on a detected signal level of the low noise amplifier, and a limiter enable circuit configured to selectively connect an output of the overload protection circuit to the analog control input based on a switch enable signal, the limiter enable circuit operable to disconnect the output of the overload protection circuit from the analog control input and turn off the input switch when the switch enable signal is in a disabled state.
10. The packaged front end module of claim 9 wherein the overload protection circuit is configured to increase the impedance of the input switch to reduce a magnitude of the radio frequency input signal in response to determining that the detected signal level indicates an overload condition.
11. The packaged front end module of claim 9 wherein the limiter enable circuit is further configured to selectively connect the output of the overload protection circuit to the analog control input based on a state of a limiter enable signal.
12. The packaged front end module of claim 9 wherein the overload protection circuit includes a detector configured to generate a detection signal indicating the detected signal level of the low noise amplifier, and an error amplifier configured to provide feedback to the analog control input based on amplifying a difference between the detection signal and a reference signal.
13. The packaged front end module of claim 9 wherein the integrated circuit further includes a bypass path electrically connected to a second throw of the input switch.
14. The packaged front end module of claim 13 wherein the integrated circuit further includes a power amplifier configured to provide an amplified radio frequency signal to a third throw of the input switch.
15. The low noise amplifier system of claim 5 wherein the overload protection circuit is configured to increase the impedance of the input switch to reduce a magnitude of the radio frequency input signal in response to determining that the detected signal level indicates an overload condition.
16. The low noise amplifier system of claim 5 wherein the detected signal level includes an output signal level of the low noise amplifier.
17. The low noise amplifier system of claim 5 wherein the detected signal level includes an internal signal level of the low noise amplifier.
18. The low noise amplifier system of claim 5 further comprising a limiter enable circuit configured to selectively connect an output of the overload protection circuit to the analog control input.
19. The low noise amplifier system of claim 18 wherein the limiter enable circuit is configured to receive a switch enable signal, and to disconnect the output of the overload protection circuit from the analog control input and turn off the input switch when the switch enable signal is in a disabled state.
20. The low noise amplifier system of claim 19 wherein the limiter enable circuit is configured to receive a limiter enable signal, and to disconnect the output of the overload protection circuit from the analog control input when the limiter enable signal is in a disabled state.