Amplifier circuit

1. An amplifier circuit, comprising:

a first bipolar transistor of which the emitter is grounded; and

a bias circuit of the first bipolar transistor,

wherein the bias circuit includes

a second bipolar transistor constituting a current mirror circuit along with the first bipolar transistor,

a first resistor connected to the bases of the first bipolar transistor and the second bipolar transistor, and

a third bipolar transistor of which the emitter is connected to the bases of the first bipolar transistor and the second bipolar transistor through the first resistor, and of which the base is connected to the collector of the second bipolar transistor,

wherein the first bipolar transistor amplifies a signal input to the base thereof and then outputs the amplified signal from the collector of the first bipolar transistor, and

a voltage is applied from a voltage source to the collector of the third bipolar transistor and the bias circuit has a second resistor connected to the collector of the third bipolar transistor.

2. The amplifier circuit according to claim 1 , wherein a current is applied from a constant current source to the collector of the second bipolar transistor and the base of the third bipolar transistor and the bias circuit has a third resistor connected to the base of the third bipolar transistor.

3. The amplifier circuit according to claim 1 , wherein the bias circuit has a fourth resistor connected to the emitter of the second bipolar transistor and the emitter of the second bipolar transistor is connected to the ground via the fourth resistor.

4. The amplifier circuit according to claim 1 , wherein a plurality of the first bipolar transistors are provided, and the plurality of first bipolar transistors are disposed in parallel to the second bipolar transistor.

5. The amplifier circuit according to claim 4 , wherein includes a plurality of the second bipolar transistors, and the plurality of second bipolar transistors are disposed in parallel to the first bipolar transistor.

6. The amplifier circuit according to claim 1 , wherein the first bipolar transistor and the second bipolar transistor are a heterostructure bipolar transistor.

7. The amplifier circuit according to claim 1 , wherein the bias circuit has a fifth resistor connected between the base of the second bipolar transistor and the first resistor.

8. The amplifier circuit according to claim 1 , wherein the bias circuit has a sixth resistor connected between the base of the first bipolar transistor and the first resistor.

9. The amplifier circuit according to claim 7 , wherein the bias circuit has a sixth resistor connected between the base of the first bipolar transistor and the first resistor.

10. The amplifier circuit according to claim 1 , wherein the amplifier circuit is an integrated circuit in which the first bipolar transistor and the bias circuit are integrated in a single chip.

11. An amplifier circuit, comprising:

a first bipolar transistor of which the emitter is grounded; and

a bias circuit of the first bipolar transistor,

wherein the bias circuit includes

a second bipolar transistor constituting a current mirror circuit along with the first bipolar transistor,

a first resistor connected to the bases of the first bipolar transistor and the second bipolar transistor, and

a third bipolar transistor of which the emitter is connected to the bases of the first bipolar transistor and the second bipolar transistor through the first resistor, and of which the base is connected to the collector of the second bipolar transistor,

wherein the first bipolar transistor amplifies a signal input to the base thereof and then outputs the amplified signal from the collector of the first bipolar transistor, and

a current is applied from a constant current source to the collector of the second bipolar transistor and the base of the third bipolar transistor and the bias circuit has a third resistor connected to the base of the third bipolar transistor.

12. The amplifier circuit according to claim 11 , wherein the bias circuit has a fourth resistor connected to the emitter of the second bipolar transistor and the emitter of the second bipolar transistor is connected to the ground via the fourth resistor.

13. The amplifier circuit according to claim 11 , wherein a plurality of the first bipolar transistors are provided, and the plurality of first bipolar transistors are disposed in parallel to the second bipolar transistor.

14. The amplifier circuit according to claim 13 , wherein includes a plurality of the second bipolar transistors, and the plurality of second bipolar transistors are disposed in parallel to the first bipolar transistor.

15. The amplifier circuit according to claim 11 , wherein the first bipolar transistor and the second bipolar transistor are a heterostructure bipolar transistor.

16. The amplifier circuit according to claim 11 , wherein the bias circuit has a fifth resistor connected between the base of the second bipolar transistor and the first resistor.

17. The amplifier circuit according to claim 16 , wherein the bias circuit has a sixth resistor connected between the base of the first bipolar transistor and the first resistor.

18. The amplifier circuit according to claim 11 , wherein the bias circuit has a sixth resistor connected between the base of the first bipolar transistor and the first resistor.

19. The amplifier circuit according to claim 11 , wherein the amplifier circuit is an integrated circuit in which the first bipolar transistor and the bias circuit are integrated in a single chip.

20. An amplifier circuit, comprising:

a first bipolar transistor of which the emitter is grounded; and

a bias circuit of the first bipolar transistor,

wherein the bias circuit includes

a second bipolar transistor constituting a current mirror circuit along with the first bipolar transistor,

a first resistor connected to the bases of the first bipolar transistor and the second bipolar transistor,

a third bipolar transistor of which the emitter is connected to the bases of the first bipolar transistor and the second bipolar transistor through the first resistor, and of which the base is connected to the collector of the second bipolar transistor, and

a capacitor connected to the collector of the second bipolar transistor,

wherein the first bipolar transistor amplifies a signal input to the base thereof and then outputs the amplified signal from the collector of the first bipolar transistor.

21. amplifier circuit according to claim 20 , wherein the bias circuit has a fourth resistor connected to the emitter of the second bipolar transistor and the emitter of the second bipolar transistor is connected to the ground via the fourth resistor.

22. The amplifier circuit according to claim 20 , wherein a plurality of the first bipolar transistors are provided, and the plurality of first bipolar transistors are disposed in parallel to the second bipolar transistor.

23. The amplifier circuit according to claim 22 , wherein includes a plurality of the second bipolar transistors, and the plurality of second bipolar transistors are disposed in parallel to the first bipolar transistor.

24. The amplifier circuit according to claim 20 , wherein the first bipolar transistor and the second bipolar transistor are a heterostructure bipolar transistor.

25. The amplifier circuit according to claim 20 , wherein the bias circuit has a fifth resistor connected between the base of the second bipolar transistor and the first resistor.

26. The amplifier circuit according to claim 25 , wherein the bias circuit has a sixth resistor connected between the base of the first bipolar transistor and the first resistor.

27. The amplifier circuit according to claim 20 , wherein the bias circuit has a sixth resistor connected between the base of the first bipolar transistor and the first resistor.

28. The amplifier circuit according to claim 20 , wherein the amplifier circuit is an integrated circuit in which the first bipolar transistor and the bias circuit are integrated in a single chip.