JPH0211044B2 - - Google Patents

Description

Detailed Description of the Invention The present invention relates to a level shift circuit that level-shifts a minute input signal applied to an input terminal by a certain DC level and then transmits it to the next stage. The purpose is to realize a circuit that operates stably even under power supply voltage.

FIG. 1 shows a circuit connection diagram of a level shift circuit according to an embodiment of the present invention. In FIG. 1, the input terminal X is connected to the base of a transistor 1, and the collector of the transistor 1 is connected to the base of a complementary transistor 2 (NPN to PNP). The emitter of the transistor 2 is connected to the negative power supply line g.
between the emitter of the transistor 1 and the collector of the transistor 2.
The emitter and base of a diode-connected transistor 3 whose collectors are short-circuited are connected. A resistor 4 as a load is connected between the collector of the transistor 2 and the output terminal Y, a constant current source 5 is connected between the positive feed line b and the output terminal Y, and the feed line b and another constant current source 6 between the emitter of the transistor 1 and the emitter of the transistor 1.
is connected.

The positive power supply line b is connected to the positive power supply terminal B, and the negative power supply line g is connected to the negative power supply terminal G.

Now, in FIG. 1, assuming that the base-emitter forward voltage of transistor 1 and the base-emitter forward voltage of transistor 3 are approximately equal, the input terminal The level of the transistor 2 becomes the same as the level of the collector of the transistor 2.

That is, if the level of the input terminal .

As a result, the base current of the transistor 2 increases, and the level of the collector of the transistor 2 decreases. Eventually, the level of the input terminal X becomes equal to the level of the collector of the transistor 2, and the transistor 1 and the The balanced state of transistor 3 is maintained.

On the other hand, a constant current I _p is supplied from the constant current source 5 to the resistor 4, and a constant voltage drop occurs across the resistor 4.

Here, when the resistance value of the resistor 4 is R and the signal voltage applied to the input terminal X is e _i , the signal voltage e _p appearing at the output terminal Y is expressed by the following equation.

e _p = e _i + I _p R Therefore, the circuit in Figure 1 has the function of DC-shifting the input signal applied to the input terminal X by a certain level and supplying it to the output terminal Y. become.

By the way, the level shift circuit shown in FIG. 1 not only has an extremely simple circuit configuration, but also can be expected to operate sufficiently stable even under a low power supply voltage of around 1.5V.

For example, a well-known current mirror circuit can be used as the constant current sources 5 and 6, and in that case, a transistor (PNP type) constituting the current mirror circuit is placed at the constant current sources 5 and 6 in FIG. Since only the collector and emitter of is connected, the voltage between the collector and emitter is
It can be operated even at around 0.3V, and the forward voltage between the base and emitter of transistor 3 in Figure 1 is around 0.7V, and when handling small signals, the voltage between the collector and emitter of transistor 2 should also be around 0.4V. is sufficient, so even if these voltages are added together, the result is about 1.4V.

Note that if the reference current for the constant current sources 5 and 6 is obtained by the circuit proposed in Patent Application No. 142720 of 1982 by the same applicant, it can be obtained with a power supply voltage as low as 1.5V. It is possible to realize a stable constant current source even at low temperatures.

Now, the embodiment of the present invention is not necessarily limited to the circuit shown in FIG. 1, and various changes can be made as necessary. For example, as illustrated in FIG. 2, if the collector of transistor 3 is connected to the negative feed line g instead of connecting to the base,
When converting the circuit into a monolithic IC, a substrate PNP transistor can be used as the transistor 3, which reduces the chip size, increases the operating gain, and improves followability.

Also, if necessary, the base of transistor 2
If a resistor 7 or the like is connected between the emitters, the leakage current of the transistor can be bypassed, so that temperature stability can be improved.

Further, as shown in FIG. 3, a simple diode 8 may be used instead of the transistor 3, and a diode 9 may be used instead of the resistor 4.

As described above, the level shift circuit of the present invention includes a first transistor (corresponding to transistor 1 in the above embodiment) whose base is connected to the input terminal, and a transistor complementary to the first transistor whose base is connected to the input terminal. connected to the collector of the first transistor;
a second transistor (corresponding to transistor 2) whose emitter is connected to one of the feed lines; and a diode means (base of transistor 3) connected between the emitter of the first transistor and the collector of the second transistor. - emitter-to-emitter junction or diode 8) and a load means (corresponding to resistor 4 or diode 9) connected between the collector of the second transistor and the output terminal.
and a first constant current means (corresponding to the constant current source 5) connected between the other feed line and the output terminal;
It is characterized by comprising a second constant current means (corresponding to the constant current source 6) connected between the other feed line and the emitter of the first transistor,
It has a very simple configuration and has the great effect of being able to operate even under a low power supply voltage.

[Brief explanation of drawings]

1, 2, and 3 are circuit wiring diagrams of level shift circuits according to each embodiment of the present invention. 1, 2, 3...Transistor, 4...Resistor,
5, 6... constant current source, 8, 9... diode.

Claims (1)

[Scope of Claims] 1. A first transistor whose base is connected to an input terminal, and which is complementary to the first transistor, whose base is connected to the collector of the first transistor, and whose emitter is connected to one of the transistors. a second transistor connected to a power supply line; diode means connected between the emitter of the first transistor and the collector of the second transistor; and between the collector of the second transistor and the output terminal. a first constant current means connected between the other feed line and the output terminal; and a second constant current means connected between the other feed line and the emitter of the first transistor. A level shift circuit characterized by comprising constant current means. 2 In the description of claim 1, the third
The base of the transistor is connected to the collector of the second transistor, the emitter of the transistor is connected to the emitter of the first transistor, and the collector is connected to one of the feed lines, and the base and emitter of the third transistor are connected to the collector of the second transistor. A level shift circuit characterized in that the diode means is constructed by a junction between the diode means.