Reference current circuit for adjusting its output current at a low power-supply voltage
View Patent ↗A reference current circuit includes a differential amplifier amplifying a difference in potential between a reference voltage and a first node and outputting the amplified potential difference to a second node, and adjusting transistors connected between a supply voltage and the first node. The reference current circuit further includes switches provided correspondingly to the adjusting transistors to apply a voltage of the second node to control electrodes of the adjusting transistors in response to control signals that are respectively input to the switches. The reference current circuit further includes a resistance connected between the first node and a common potential, and an output transistor having its conduction state responsive to the voltage of the second node for controlling a current supplied from the supply voltage to a load.
1. A reference current circuit comprising:
a differential amplifier for amplifying a difference in potential between a reference voltage and a first node, and outputting an amplified potential difference to a second node;
a plurality of adjusting transistors connected between a supply voltage and said first node;
a plurality of switches provided correspondingly to said plurality of adjusting transistors for applying a voltage of said second node to control electrodes of said adjusting transistors in response to control signals that are respectively input to said switches;
a resistance connected between said first node and a common potential; and
an output transistor having a conduction state responsive to the voltage of said second node for controlling a current that is supplied from the supply voltage to a load.
2. The reference current circuit in accordance with claim 1 , wherein said plurality of adjusting transistors have dimension sizes different from each other so that each of said plurality of adjusting transistors has current-drivability satisfying a relationship of minus n-th power of two, among said plurality of adjusting transistors, where n is a positive integer.
3. The reference current circuit in accordance with claim 1 , wherein said plurality of adjusting transistors are of a same size as each other and form serial connections which are different in number of said transistors from each other.
4. The reference current circuit in accordance with claim 3 , wherein the serial connections are different in number of said transistors from each other in a relationship of n-th power of two, where n is a positive integer.
5. A reference current circuit comprising:
a first differential amplifier for amplifying a difference in potential between a reference voltage and a first node, and outputting an amplified potential difference to a second node;
a plurality of adjusting transistors connected between a supply voltage and said first node;
a plurality of switches provided correspondingly to said plurality of adjusting transistors for applying a voltage of said second node to control electrodes of said adjusting transistors in response to control signals that are respectively input to said switches;
a first resistance connected between said first node and a common potential;
a first output transistor having a conduction state responsive to the voltage of said second node for controlling a first current that is supplied from the supply voltage to an output node;
a second differential amplifier for amplifying a difference in potential between the reference voltage and a third node, and outputting an amplified potential difference to a fourth node;
a first control transistor connected between the supply voltage and a fifth node to which the reference voltage is output, and having a conduction state responsive to a voltage of said fourth node;
a first diode connected between said fifth node and the common potential;
a second control transistor connected between the supply voltage and said third node, and having a conduction state responsive to the voltage of said fourth node;
a second resistance connected between said third node and a sixth node;
a second diode connected between said sixth node and the common potential, and having current-carrying capacity higher than said first diode; and
a second output transistor having a conduction state responsive to the voltage of said fourth node for controlling a second current that is supplied from the supply voltage to said output node.
6. The reference current circuit in accordance with claim 5 , wherein said plurality of adjusting transistors have dimension sizes different from each other so that each of said plurality of adjusting transistors has current-drivability satisfying a relationship of minus n-th power of two, among said plurality of adjusting transistors, where n is a positive integer.
7. The reference current circuit in accordance with claim 5 , wherein said plurality of adjusting transistors are of a same size as each other and form serial connections which are different in number of said transistors from each other.
8. The reference current circuit in accordance with claim 7 , wherein the serial connections are different in number of said transistors from each other in a relationship of n-th power of two, where n is a positive integer.