JPS6239567B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multi-channel power IC such as a dual power IC (semiconductor integrated circuit).

Since a dual power IC has two sets of the same circuit, it is conceivable to use various bias circuits in common in order to simplify the circuit.

When the constant current circuit that forms the constant current load of the drive stage class A amplifier circuit or the bias current of the output stage B class pushpull circuit constituting the above power IC is configured with a current mirror circuit connected to the bootstrap power supply line, the above Since the bootstrap power supply line fluctuates depending on the output voltage of its channel, if a common constant current is distributed through transistors and used as the input current of the current mirror circuit of each channel, the voltage of this distribution transistor is Since the collector current varies depending on the bootstrap power supply line, the equivalent resistance between the collector and emitter of these transistors (output admittance h
_pe ), the common emitter potential of the distribution transistor fluctuates, which significantly worsens the crosstalk between channels.

This invention was made in order to provide a multi-channel power IC with a simplified bias circuit without worsening crosstalk between channels.

This invention lowers the conductance gm of these distribution transistors by providing a resistor at the emitter of the transistor that distributes constant current,
It distributes a common constant current.

Hereinafter, this invention will be explained in detail along with examples.

The drawing is a circuit diagram of a dual power IC showing an embodiment of the present invention.

In the figure, all circuit elements surrounded by dotted lines are formed within one semiconductor chip by a well-known semiconductor integrated circuit manufacturing method.

1 is a stabilized power supply circuit, which uses a constant voltage formed by a constant voltage element such as a Zener diode to control the stabilized power supply for the first stage amplifiers 2, 2' and the bias current necessary for the operation of the first stage amplifiers 2, 2. It is something that forms.

Input signals passed through external input terminals P ₀ , P 0 ' are applied to the non-inverting input terminals (+) of the first stage amplifiers 2, 2', and resistors R ₅ , P ₀ ' are applied to the inverting input terminals (-).
R ₆ (R ₅ ′, R ₆ ′), constant current circuit I ₀ (I ₀ ′) and terminal P ₁
The output of the output terminal P ₄ (P 4 ′) of the output stage push-pull circuit is transmitted through the negative feedback circuit composed of the capacitor C ₂ (C ₂ ′) connected to the output terminal P ₄ (P ₄ ′). Accordingly, the AC voltage gain of the output stage push-pull circuit is determined, and the output DC voltage level thereof is determined to be approximately Vcc/2.

The output signal of the first stage amplifier 2 is transmitted through a drive stage consisting of Darlington-connected transistors Q ₇ and Q ₈ , a resistor R ₇ , a phase compensation capacitor C ₁ , a diode-connected transistor Q ₉ , and a constant current load transistor Q ₅ It is amplified by a class A amplifier circuit.

This drive stage amplified output is supplied to transistors Q ₁₄ and Q ₁₅ connected in a Darlington configuration that constitute an output stage B class push-pull circuit, and
Transistors connected in complementary form
It is also supplied to Q ₁₆ and Q ₁₇ . The emitter of the transistor Q ₁₆ is connected to an idling current adjustment circuit composed of a diode or diode-connected transistors Q ₁₁ to _{Q 13} and a transistor Q ₁₀ to reduce crossover distortion of the push-pull output circuit. be able to.

Constant current load transistor of drive stage class A amplifier circuit
The base of _Q5 and the base of the constant current transistor _Q6 of the idling current adjustment circuit are commonly connected to the base of the input side transistor _Q4 constituting the current mirror circuit.

Each of the circuits configured above is omitted since the drive stage class A amplifier circuit and the output stage B class push pull circuit B of the other channel are completely the same circuits.

Furthermore, in order to increase the output amplitude, the output stage B-class push-pull circuit uses the constant current transistors Q ₄ to Q ₆ (Q ₄ ′ to Q ₆ ′) and the drive transistor Q _{14 .}
The supply voltage line to which is connected is terminal P ₂ (P ₂ ′)
Boot-trap capacitors C ₃ and C ₃ ' are provided between the output terminal P ₄ (P _{4 ') and the output terminal P 4 (P 4} ').

In this embodiment, in order to share the bias circuit that controls the current mirror circuit, a resistor is used.
Transistor formed by R ₄ and transistor Q ₁
Connect the resistor R ₁ to the constant current terminal between the base and emitter of Q ₁ .
By providing a constant current, a constant current is caused to flow through this resistor R ₁ , and the transistors Q 2 and Q 3 whose base is commonly applied to the collector of the transistor Q ₁ and resistors R ₂ and _{R 3} are provided at their emitters, _respectively , ,
The respective collector currents to which the constant current formed above is distributed are connected to the current mirror circuits Q ₄ to Q ₆ (Q ₄ ′ to
Q ₆ ′) input bias current.

In this bias circuit, the emitters of transistors Q ₂ and Q ₃ that distribute constant current have resistances, so these transistors Q ₂ and
Since the conductance gm (gain) of Q ₃ decreases, even if the collector voltages of the transistors Q ₂ and Q ₃ change with the bootstrap voltage, the gains of the signal paths transmitted to the other channel are significantly reduced. Therefore, even if the bias circuit is shared and the circuit is simplified, an increase in crosstalk can be prevented.

By the way, when the bias current is set to 1 mA, crosstalk can be improved by 10 dB by setting _{the resistors R 2 and} R ₃ to about 52 Ω _. Since it is not required, it can be configured with a small footprint on a monolithic semiconductor chip.
The circuit can be simplified.

The present invention is not limited to the embodiment described above, and the constant current circuit that generates the reference constant current can be modified in various ways. For example, a resistor may be provided at the emitter of the transistor _Q1 .

The present invention can be widely used in multi-channel power ICs in which a constant current transistor in a drive stage or an output stage is provided in a boot-trap power supply line.

[Brief explanation of the drawing]

The drawing is a circuit diagram showing an embodiment of the present invention. 1... Stabilized power supply circuit, 2, 2'... First stage amplifier,
3...Drive stage and output stage circuit of the other channel.

Claims (1)

[Claims] 1. A bootstrap power supply line, a constant current bias transistor, a load means connected between the bootstrap power supply line and the collector of the constant current bias transistor, and a base-emitter voltage generated in the load means. a common circuit that supplies a common bias voltage to the constant current bias transistors of the first and second power amplifier circuits; A multi-channel power IC including a bias circuit, wherein the common bias circuit includes a first resistor whose one end is connected to a reference potential point of the circuit;
second and third resistors connected between the other ends of the resistors and the emitters of the constant current bias transistors of the first and second power amplifier circuits, and the voltage generated in the first resistor as a base. - a first transistor whose base and emitter are connected to the first resistor so as to be received between the emitters, and whose collector is connected to the bases of the constant current bias transistors of the first and second power amplifier circuits; biasing means connected to the collector of the first transistor.