US 12,455,586 B1
Current source circuits tolerant of transistor characteristics variations
Yutaka Saeki, Kanagawa (JP)
Assigned to Synaptics Incorporated, San Jose, CA (US)
Filed by Synaptics Incorporated, San Jose, CA (US)
Filed on Sep. 3, 2024, as Appl. No. 18/822,942.
Int. Cl. G05F 3/26 (2006.01); G09G 3/20 (2006.01); G09G 3/3275 (2016.01); H03K 17/687 (2006.01)
CPC G05F 3/262 (2013.01) [G09G 3/2096 (2013.01); H03K 17/687 (2013.01); G09G 3/2007 (2013.01); G09G 3/3275 (2013.01); G09G 2310/0291 (2013.01); G09G 2310/08 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A current source circuit, comprising:
a plurality of current generation subcircuits, wherein each of the plurality of current generation subcircuits comprises:
an output transistor comprising a drain through which an output constant current is generated;
a resistor coupled between a first constant voltage node and a source of the output transistor; and
a storage capacitor coupled between the first constant voltage node and a gate of the output transistor; and
a first operational amplifier comprising:
a first input coupled to a second constant voltage node;
a second input selectively couplable to the source of the output transistor; and
an output selectively couplable to the gate of the output transistor.
 
16. A display driver, comprising:
a current source circuit comprising:
a plurality of current generation subcircuits, wherein each of the plurality of current generation subcircuits comprises:
an output transistor comprising a drain through which an output constant current is generated;
a resistor coupled between a first constant voltage node and a source of the output transistor; and
a storage capacitor coupled between the first constant voltage node and a gate of the output transistor; and
a first operational amplifier comprising:
a first input coupled to a second constant voltage node;
a second input selectively couplable to the source of the output transistor; and
an output selectively couplable to the gate of the output transistor; and
panel drive circuitry configured to drive a display panel using the output constant currents generated by the plurality of current generation subcircuits.
 
19. A method of operating a current source circuit comprising a plurality of current generation subcircuits, the method comprising:
driving a gate of an output transistor of each of the plurality of current generation subcircuits, wherein each of the plurality of current generation subcircuits comprises a resistor coupled between a first constant voltage node and a source of the output transistor, and wherein the driving of the gate of the output transistor of each of the plurality of current generation subcircuits is based on a voltage between a second constant voltage node and the source of the output transistor of each of the plurality of current generation subcircuits;
holding, by a storage capacitor coupled between the first constant voltage node and the gate of the output transistor in each of the plurality of current generation subcircuits, a gate voltage of the output transistor in each of the plurality of current generation subcircuits; and
generating an output constant current through a drain of the output transistor of each of the plurality of current generation subcircuits.