US 12,034,411 B2
Method of improving linearity of amplifier circuit including magnetically coupled feedback loop and DC bias current adjustment without impacting amplifier gain
Ali Fard, Corona Del Mar, CA (US); and Mats Carlsson, Sundbyberg (SE)
Assigned to QuantalRF AG, Zurich (CH)
Filed by QuantalRF AG, Zurich (CH)
Filed on Sep. 27, 2021, as Appl. No. 17/486,417.
Claims priority of provisional application 63/084,497, filed on Sep. 28, 2020.
Prior Publication US 2022/0102070 A1, Mar. 31, 2022
Int. Cl. H03F 1/34 (2006.01); H01F 38/14 (2006.01); H03F 1/32 (2006.01); H03F 3/21 (2006.01); H03F 3/24 (2006.01)
CPC H03F 1/32 (2013.01) [H01F 38/14 (2013.01); H03F 1/3229 (2013.01); H03F 1/3247 (2013.01); H03F 1/347 (2013.01); H03F 3/21 (2013.01); H03F 3/24 (2013.01); H03F 2200/09 (2013.01); H03F 2200/451 (2013.01); H03F 2200/534 (2013.01); H03F 2200/541 (2013.01)] 12 Claims
OG exemplary drawing
 
1. A method of operating an amplifier circuit having a transformer arranged so as to establish a magnetically coupled feedback loop between an output of an amplifier and an input of the amplifier, the method comprising:
providing a DC bias current to the amplifier wherein a transfer gain of the amplifier circuit depends only on the characteristics of the transformer and is substantially independent of signal level and of inherent gain characteristics of the amplifier when a loop gain of the magnetically coupled feedback loop is at least 10 dB; and
increasing the DC bias current to improve a linearity of the amplifier circuit wherein the transfer gain of the amplifier circuit remains constant when the DC bias current is increased.