JPH01272306A - Starting circuit for current source circuit - Google Patents

Abstract

PURPOSE:To attain stable driving at a low voltage by providing the title circuit with 1st and 2nd circuits constituted under a prescribed condition and a diode characteristic element and fixing the saturated current value of the circuit on a prescribed value. CONSTITUTION:The circuit is constituted of the 1st circuit having the serial connection of diodes (Dod) 2, 3 or current voltage characteristic equivalent to the serial connection, the 2nd circuit consisting of a current mirror constituted of transistors(TR) 11-14 and the Dod characteristic element 5. Immediately after applying power supply voltage in said constitution, the collector current of the TRs 11-14 is zero. When saturated current values of the Dod 5 and between the bases and emitters of the TRs 11, 12 are set up to values equal or larger to/than that of the Dod 2, 3, current flowing into a resistor 1 is branched into the the circuit constituted of the serial circuits consisting of the Dod 2, 3, the Dod 5, the TRs 11, 12, and resistors 4, 15. Thereby, the collector current of respective TRs is started to flow, increased and stabilized at an operation point of the current source circuit constituted of the TRs 11-14 and the resistors 4, 15-17.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention particularly relates to a starting circuit for a current source circuit driven at a low voltage.

[Summary of the invention]

The present invention relates to a starting circuit for a current source circuit, and is capable of driving at a lower voltage by determining the saturation current value of the circuit.

[Conventional technology]

For example, there is a current source circuit used in a monolithic IC as shown in FIG. That is, in the figure,
A first current mirror consisting of NPN) transistor α(2) and a second current mirror consisting of PNP transistor (c) α→
A current mirror B is combined and provided between the first power supply VCC and the second power supply [GND, and the emitter size of the transistor (6) is made to be more than twice that of the transistor (11), and the transistor (6) A predetermined emitter resistance (c) is provided at transistor (2), and a mutually equal emitter resistance α* (1) is provided at transistor (2) α◆.

When this current source circuit is driven by this, a current is caused to flow through this circuit, and this current can be taken out by further connecting a transistor to the first or second current mirror.

However, in this circuit, the stable operating point of the circuit may be a state where the current is 0, in addition to the state where the desired current is flowing as described above. When the power source is turned on, a stable point of zero current is maintained, and there is a possibility that the desired current cannot be obtained.

Therefore, conventionally, as shown in the figure, for example, the first power supply VC
100 kΩ between C and the connection midpoint of the current mirror ■
A small amount of current is supplied through this high resistance (100) t when the power is turned on, etc., so that the desired current flows. .

[Problem to be solved by the invention]

However, when the above-mentioned high resistance (100)'t- is provided, 1) the high resistance (100) is connected to the power supply Vcc during operation of the current source circuit;
00)', a ripple current flows in, and the stability of the current source output against ripples deteriorates.

2) Ninth IC, which usually requires a resistance on the order of 100Ω
The area occupied by this high resistance (Zoo) within the chip becomes extremely large. In addition, to save area, tunnel resistance and F
Although it is possible to use ETf, these semiconductor resistors have large manufacturing variations, resulting in large variations in stability against ripples.

There were problems such as.

In response to this, a startup circuit has been proposed that uses a diode or the like to shut off the circuit after startup.

(Gray + M@yor “Analysts a
nd Design of Analog Int@gr
at@d C1rcults” 1977 t Joh
However, in the case of this circuit, since a circuit in which a large number of diodes are connected in series is used as a starting circuit, at least the sum of the head direction voltages of these diodes is used as the power supply vcc. This required a voltage exceeding 100%, making it unsuitable for low-voltage drive circuits.

This application was filed in view of these points.

[Ninth means to solve all problems]

The present invention includes a resistor (1) that supplies the entire current from the first power supply Vcc to the first node (2), and two diodes (2) (3) connected from the first node to the second power supply GND. A first circuit with series connection or equivalent current-voltage characteristics, NPN current mirror α1) (6) and P
A resistor (4) is fully inserted in series with one current path (■) of a current source circuit consisting of a combination of NP current mirrors α3 (14), and the current between the second circuit, the first node, and one of the above It consists of a diode characteristic element (5) connected between the passages, and is characterized in that the saturation current value of the first circuit is equal to or smaller than the saturation current value of the second circuit and the diode characteristic element. This is a starting circuit for a current source circuit.

[Effect]

According to this, there is no need to use a high resistance, so there is no risk of occupying a large area within the IC chip, and by determining the saturation current value of the circuit, it is possible to stably drive the circuit at a lower voltage.

〔Example〕

In Figure 1, the power supply VCC is resistor (1)'! ! − is connected to the node ■ through the diode (
2) Connected to the power supply GND via the series connection of (3). A resistor (4) is inserted into one current path (2) of a current source circuit consisting of transistors α2 to α→, and a diode (5) is provided between the above-mentioned node (2) and the current path (2).

Therefore, in this circuit, resistors (1) (4) and diodes (21 (3) (5)) are the starting circuit.

Immediately after the power supply voltage is applied in this circuit,
The collector current of each transistor α■ to α4 is O.

At this time, diode (5), transistor α (2)
If the saturation current value of the base-emitter characteristics of the total diode (2) (3) is made equal to or larger than the saturation current value of the base-emitter characteristic, the current passing through the resistor (1) will be the same as the saturation current value of the diode (2) (3).
The current is shunted into a circuit consisting of a series circuit of (3) and a diode (5) a resistor (4) a transistor 0D base-emitter junction and a base-emitter junction of transistor 0 and a resistor (T).

For this reason, the collector current of each transistor begins to flow,
Increasing the transistor ◇ ~ α4 resistance) ~ α power (4)
It is stabilized at the operating point of the current source circuit configured by . After the operating point of the circuit is stabilized, transistor α is added to resistor (4).
A current equal to the sum of the emitter current ■□ of → and the base current I, 2 of the transistor (6) flows.

Here, diode +2) Characteristics of voltage and current applied to the series circuit of (3) i C1, diode (5) resistance (4
) Transistor, Zostar 01) (6) (collector open), circuit consisting of 0 resistors (see Figure 2)
The characteristics of the voltage and current applied to the circuit are shown in FIG. 3 as 02.

Therefore, in this diagram, it is possible to set the operating point in a region where the current of C1 rises and the current of C2 does not rise. As a specific example, resistance (4) is 4.5Ω,
Assuming that the resistor a is 360 Ω, the resistor α → -resistance (Lη), the emitter size of the transistor (6) is quadrupled, and the saturation current of the transistor (NPN and diode) is equal, the emitter current of the transistor (11) is Approximately 100
With μA, the potential drop across the resistor (4) is approximately 450 mV. As a result, a voltage approximately 450 mV lower than the forward rising voltage is applied to the diode (5). At this time, the current flowing through the diode (5) becomes a value that can be ignored in terms of the current flowing through the diode (2).

In other words, by assuming the operating point as described above,
After the circuit has started up, connect the diode (5) from Vcc.
This eliminates the possibility of power supply ripples entering the circuit, greatly improving stability.

In this way, according to the above-mentioned circuit, there is no need to use a high resistance, so there is no need to use a large area in the C chip, and by determining the saturation current value of the circuit, stable driving can be achieved at a lower voltage. be able to.

In the above circuit, the series circuit of diodes (2) and (3) may have a different configuration as long as it has the same current-voltage characteristics.

Further, the current mirror formed by the transistor [alpha] and the negative four resistors [alpha] and [alpha] may also have other configurations as long as they have the same characteristics.

Further, the diode (5) also has diode characteristics, and n may be another element. In particular, in order to increase the saturation current value, a diode-connected element with a transistor with a larger emitter size may be used.

It is also clear that the same operation can be realized even if a complementary circuit configuration is used in the above-mentioned circuit.
There is no risk of occupying a large area within the circuit, and by determining the saturation current value of the circuit, stable driving can be performed at a lower voltage.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an example of the present invention, FIGS. 2 and 3 are the ninth diagrams for explaining the same, and FIG. 4 is the ninth diagram for explaining the conventional technique. (1) (4) (b) - α is resistance, (2) (3)
(51 is a diode, (1]) ~ α4 is a transistor,
vccS GND is a power supply.

Claims (1)

[Claims] A resistor that supplies current from a first power source to a first node, and two diodes connected in series from the first node to a second power source, or a current-voltage equivalent thereto. a first circuit having a characteristic, a second circuit in which a resistor is inserted in series in one current path of a current source circuit configured by a combination of an NPN current mirror and a PNP current mirror, and the first node and the above. It consists of a diode characteristic element connected between one current path, and is characterized in that the saturation current value of the first circuit is equal to or smaller than the saturation current value of the second circuit and the diode characteristic element. Starting circuit for current source circuit.