JPH08340243A - Bias circuit - Google Patents

Abstract

PURPOSE: To improve relative accuracy without being affected by wiring resistance or the like between plural circuit blocks by supplying an output of a current mirror circuit in a certain circuit block to other circuit blocks including current mirror circuits. CONSTITUTION: A base current is supplied from a bipolar transistor(TR) 17 to bipolar TRs 8 to 10 in a circuit block 1 to constitute a current mirror. A current supplied from a current source 7 and mirrored by the block 1 is mirrored by other circuit blocks 2 to 4 and used for circuits in respective circuit blocks. For instance, a current supplied from the collector of the TR 8 to the circuit block 2 is converted into the bias voltage of the current mirror by a TR 11 and the bias voltage is supplied to the bases of other bipolar TRs 13 to 15 constituting a current mirror. The base current of the bipolar TRs constituting the current mirror is supplied from a MOS TR 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a bias circuit,
In particular, the present invention relates to a bias circuit that realizes a current mirror with high relative accuracy in a plurality of circuit blocks in an IC.

[0002]

2. Description of the Related Art Conventionally, a configuration shown in FIG. 2 has been adopted as a bias circuit for supplying a bias of the same current value in a plurality of circuit blocks. That is, as shown in FIG. 2, the bias voltage of the bias circuit formed in the circuit block 1 is supplied to the other circuit blocks 2, 3, 4, ... Bias current is generated in each circuit block.

[0003]

However, in the above-mentioned conventional bias circuit, the wiring 16 for supplying the bias voltage is used.
Since a voltage drop occurs due to the wiring resistance of the power supply wiring 6 and the wiring resistance of the power supply wiring 6, the relative accuracy of the bias current of each circuit block is determined by the layout element such as the layout of each circuit block on the IC and the wiring resistance between the circuit blocks. There was a problem that was worse.

An object of the present invention is to realize a bias circuit with high relative accuracy, which is not affected by the wiring resistance between circuit blocks and the current value mirrored in the circuit block.

[0005]

A bias circuit according to the present invention comprises a circuit block having a first current mirror circuit and a second current mirror circuit to which an output current of the first current mirror circuit is supplied. And a plurality of other circuit blocks each having

[0006]

According to the present invention, since the output of the current mirror circuit in one circuit block is supplied to another circuit block, a current that does not depend on the value of the wiring resistance between the circuit blocks can be supplied.

Further, by configuring the current mirror circuit in each of the other plurality of circuit blocks, it becomes possible to minimize the influence of the wiring resistance of the bias line for biasing the elements constituting the current mirror.
A current mirror with high relative accuracy can be realized.

In the present invention, if a bipolar transistor is used for the current mirror circuit of another circuit block, a current mirror circuit having a higher output impedance can be constructed as compared with the case where an insulated gate transistor is used. Further, by supplying the base current of the bipolar transistor forming the current mirror by the insulated gate transistor, it is possible to realize a bias with high relative accuracy that is not affected by the current value of the mirror in each circuit block.

[0009]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a circuit configuration diagram showing an embodiment of a bias circuit of the present invention, in which 1 is a circuit block containing a current mirror circuit for supplying a current to another circuit block,
2, 3, 4 are other circuit blocks to which current is supplied by the circuit block 1, 5 is a first power supply line, 6 is a second power supply line, 7 is a current source which is a source of mirrored current, 8,
9 and 10 are bipolar transistors forming a current mirror that supplies current to the other circuit blocks 2, 3 and 4.
Reference numeral 11 is a bipolar transistor for generating a bias for mirroring the current supplied to the circuit block, 13, 14, 15 are bipolar transistors for supplying the mirrored current to the circuits in the circuit block, 1
Reference numeral 2 is a MOS transistor which is an insulated gate type transistor which supplies a base current of a bipolar transistor forming a current mirror.

The current supplied from the current source 7 is supplied to the other circuit blocks 2, 3 and 4 by the current mirror circuit in the circuit block 1. Here, the base currents of the bipolar transistors 8, 9 and 10 forming the current mirror are supplied by the bipolar transistor 17, but a MOS transistor may be used as the base current supply transistor. In that case, the output current of the current mirror circuit of the circuit block 1 is not affected by the base current of the transistor that supplies the base current. Further, the current source 7 can be used from a simple type in which a resistor is inserted between a certain voltage and a complex type such as a variable current source that can be adjusted externally. Don't answer.

The current mirrored in the circuit block 1 is supplied to the other circuit blocks 2, 3, 4 ... The current supplied to each circuit block 2, 3, 4 ... Is mirrored in each circuit block and used for the circuit in each circuit block. For example, the current supplied from the collector of the transistor 8 to the circuit block 2 is converted into the bias voltage of the current mirror by the transistor 11, and the other bipolar transistors 13, 14, which form the current mirror,
A voltage is supplied to the bases of 15 ... Further, the base current of the bipolar transistor forming the current mirror is supplied by the MOS transistor 12. The transistors forming the current mirror shown in the circuit blocks 1 and 2 are bipolar transistors.
This is because the relative accuracy can be improved compared to the case where the OS transistor is used and the case where the output impedance can be increased and the MOS transistor which generally occupies the same area. A resistor is inserted between the emitter of the bipolar transistor forming the current mirror and the power supply in order to further increase the output impedance of the current mirror and further improve the relative accuracy. Whether or not to set the resistance value is determined by the accuracy of the current, the range of the collector potential of the bipolar transistor forming the mirror, the noise specification of the current, and the like. Transistors 11, 13, 14 forming the current mirror,
The base current of 15 ... Is supplied by the MOS transistor 12. Therefore, the plurality of circuit blocks 2, 3, 4 ...
The current value of each of the current mirrors is not affected by the number of transistors to be mirrored in the current mirror circuit of each circuit block. For example, the circuit blocks 2, 3 and 4 are filters using a g _m amplifier,
Consider the case where the output current of the current mirror is used as a current source that determines g _{m of the} g _m amplifier. In this case, if the characteristics required for each filter are different,
The current value mirrored by the current mirror often differs. At this time, if it is attempted to supply the base current of the bipolar transistor that constitutes the current mirror by the bipolar transistor, the base current of the transistor causes
There is an error in the mirrored current. Therefore, when the value of the current source 7 is adjusted to try to adjust the filter f _c , the characteristics of the circuit blocks 2, 3, 4, ...

According to the present invention, since the base current of the bipolar transistor forming the current mirror is supplied by the MOS transistor, each circuit block 2,
It is possible to increase the relative accuracy of the current value of the current mirror of each circuit block regardless of the number of current mirrors of 3, 4 ,.

[0014]

As described above, according to the present invention,
It is possible to increase the relative accuracy of the values of the current mirrors of a plurality of circuit blocks. This gives, for example, g _m
When used in a filter that uses an amplifier, it is possible to increase the relative accuracy of the characteristics of each filter. If you try to adjust f _c of the filter by the bias current of the g _m amplifier, the characteristics of each filter will be accurate. It becomes possible to adjust. Further, when an IC using this circuit is laid out, it is not affected by the wiring resistance between the circuit blocks, so that the degree of freedom in layout is increased, the layout time can be shortened, and the performance can be improved.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of a bias circuit of the present invention.

FIG. 2 is a circuit configuration diagram of a conventional bias circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 1st circuit block 2-4 4th 2nd-4th circuit block 5 1st power supply line 6 2nd power supply line 7 Current source 8-10 Transistor 11, 13-15 which comprises 1st current mirror Bipolar transistor 12 forming a current mirror 2 MOS transistor 16 forming a second current mirror 16 Bias voltage wiring

Front page continuation (72) Inventor Yasushi Matsuno 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (2)

[Claims] 1. A circuit block having a first current mirror circuit, and a plurality of other circuit blocks each having a second current mirror circuit to which an output current of the first current mirror circuit is supplied. Bias circuit provided. 2. The bias circuit according to claim 1, wherein
The second current mirror circuit is a bias circuit including a bipolar transistor that mirrors a current and an insulated gate transistor that supplies a base current of the bipolar transistor.