Fast wide output range CMOS voltage reference
View Patent ↗A circuit is disclosed that compensates for changes in temperature as well as for fluctuations in a supply voltage (Vcc) so that voltage reference values generated thereby are maintained at substantially constant levels irrespective of changes in temperature or fluctuations in supply voltage. The circuit is also configured to produce a wide range of voltage reference values so that it can independently service the needs of many different applications. Additionally, the circuit is designed using meal oxide semiconductor (MOS) technology, as opposed to more conventional bipolar technology, so that it “settles down” or generates reference values relatively quickly.
1. A circuit for generating a voltage reference, comprising:
a first stage comprising;
a first resistor operatively coupled to a supply voltage Vcc, and
a first transistor operatively coupled to the first resistor and to ground;
a second stage comprising;
an operational amplifier, a positive input terminal of which receives a first voltage V 1 from the first stage,
a second transistor driven by the operational amplifier,
a second resistor, a first end of which is operatively coupled to the second transistor and back to a negative input terminal of the operational amplifier, and a second end of which is coupled to ground, and
a third transistor operatively coupled to the second transistor and to the supply voltage, where a second voltage V 2 is developed at the first end of the second resistor; and
a third stage comprising;
a fourth transistor operatively coupled to the third transistor of the second stage so as to establish a current mirror arrangement such that a third current I 3 developed in the third stage is a function of a second current I 2 developed in the second stage, and
a fifth transistor operatively coupled to the fourth transistor and to ground, which outputs one or more voltage reference values that are a function of the third current I 3 ,
the current mirror arrangement comprising a cascode current mirror arrangement to further mitigate sensitivity to fluctuations in the supply voltage, the cascode current mirror arrangement comprising;
a sixth transistor operatively coupled to the third transistor, and
a seventh transistor operatively coupled to the fourth transistor as well as the sixth transistor; and
a second current mirror arrangement for providing a bias current Ib to the operational amplifier.
2. A circuit for generating a voltage reference, comprising:
a first stage comprising;
a first resistor operatively coupled to a supply voltage Vcc, and
a first transistor operatively coupled to the first transistor and to ground;
a second stage comprising;
an operational amplifier, a negative input terminal of which receives a first voltage V 1 from the first stage,
a second transistor operatively coupled to the supply voltage Vcc and driven by the operational amplifier, and
a second resistor, a first end of which is operatively coupled to the second transistor and back to a positive input terminal of the operational amplifier, and a second end of which is coupled to ground, where a second voltage V 2 is developed at the first end of the second resistor; and
a third stage comprising;
a fourth transistor operatively coupled to the second transistor and to the supply voltage Vcc, and also driven by the operational amplifier, and
a fifth transistor operatively coupled to the fourth transistor and to ground, the fifth transistor outputting one or more voltage reference values that are a function of a third current I 3 developed in the third stage.
3. The circuit of claim 2 , wherein at least one of;
the first transistor is a diode connected transistor,
the first transistor is an n type transistor,
the second transistor is a p type transistor,
the fourth transistor is a p type transistor, and
the fifth transistor is an n type transistor.
4. The circuit of claim 2 , wherein at least one of;
the first resistor and the first transistor are tuned to mitigate sensitivity of the voltage reference values to fluctuations in the supply voltage Vcc,
at least one of the first resistor, the first transistor and the second resistor are tuned to mitigate temperature sensitivity so that voltage reference values output by the circuit are substantially invariant to changes in temperature,
the voltage reference values swing from about the lowest threshold voltage (Vt) in the circuit to about Vcc, and
the circuit settles within a period of about four to about nine nanoseconds of applying Vcc.
5. A circuit for generating a voltage reference, comprising:
a first stage comprising;
a first resistor operatively coupled to a supply voltage Vcc, and
a first transistor operatively coupled to the first resistor and to ground;
a second stage comprising;
an operational amplifier, a negative input terminal of which receiving a first voltage V 1 from the first stage,
a second transistor operatively coupled to the supply voltage Vcc and driven by the operational amplifier, and
a second resistor, a first end of which is operatively coupled to the second transistor and back to a positive input terminal of the operational amplifier, and a second end of which is coupled to ground, where a second voltage V 2 is developed at the first end of the second resistor; and
a third stage comprising;
a fourth transistor operatively coupled to the second transistor and to the supply voltage Vcc, and also driven by the operational amplifier, and
a third resistor, a first end of which is operatively coupled to the fourth transistor and a second end of which is operatively coupled to ground, one or more voltage reference values generated by the circuit being developed at the first end of the third resistor, the voltage reference values being a function of a third current I 3 developed in the third stage.
6. The circuit of claim 5 , wherein at least one of;
the first transistor is a diode connected transistor,
the first transistor is an n type transistor,
the second transistor is a p type transistor, and
the fourth transistor is a p type transistor.
7. The circuit of claim 5 , wherein at least one of;
the first resistor and the first transistor are tuned to mitigate sensitivity of the voltage reference values to fluctuations in the supply voltage Vcc,
at least one of the first resistor, the first transistor and the second resistor are tuned to mitigate temperature sensitivity so that voltage reference values output by the circuit are substantially invariant to changes in temperature,
the voltage reference values swing from about ground to about Vcc, and
the circuit settles within a period of about four to about nine nanoseconds of applying Vcc.
8. The circuit of claim 5 , wherein the third current is a function of a second current I 2 developed in the second branch.