US 7,514,980 B2
Exponential function generator and variable gain amplifier using the same
Jeong Ki Choi, Kyungki-do (Korea, Republic of); Won Jin Baek, Kyungki-do (Korea, Republic of); Hyun Hwan Yoo, Seoul (Korea, Republic of); and Seung Min Oh, Kyungki-do (Korea, Republic of)
Assigned to Samsung Electro-Mechanics Co., Ltd., Suwon, Kyungki-Do (Korea, Republic of)
Filed on May 26, 2006, as Appl. No. 11/420,728.
Claims priority of application No. 10-2005-0054496 (KR), filed on Jun. 23, 2005.
Prior Publication US 2006/0290417 A1, Dec. 28, 2006
Int. Cl. G06F 7/556 (2006.01); G06G 7/20 (2006.01); G06G 7/24 (2006.01)
U.S. Cl. 327—346  [327/347; 327/348; 327/349; 327/543] 16 Claims
OG exemplary drawing
 
1. An exponential function generator for generating a current that is changed exponentially according to a control voltage, comprising:
a voltage-current converter for converting the control voltage into a current;
1st to nth curve generators, each for mirroring the current outputted from the voltage-current converter and to output a current corresponding to a predetermined ratio of an input current of the voltage-current converter to the current outputted from the voltage-current converter, where n is a natural number greater or equal to 2; and
an output end for summing up the current outputted from each of the 1st to nth curve generators to output a resultant current;
wherein the ratios of the input current to the output current of the 1st to nth curve generators are different from each other; and
wherein each of the 1st to nth curve generators comprises:
a first current mirror for receiving the current outputted from the voltage-current converter to output a current corresponding to a predetermined ratio to the current received from the voltage-current converter;
a second current mirror for receiving the current outputted from the first current mirror to output a current corresponding to a predetermined ratio to the current received from the first current mirror; and
a third current mirror for receiving the current outputted from the second current mirror to output a current corresponding to a predetermined ratio to the current received from the second current mirror.