JPS62203418A - Level shift circuit - Google Patents

Abstract

PURPOSE:To attain the level shift without driving the operating point of the titled circuit operated at a low power supply system to a region giving saturation or lowering the speed by increasing/decreasing the current of a current source of an emitter follower used for the level shift proportional to a voltage difference of a different power supply system. CONSTITUTION:Let a voltage of the 1st power terminal 1 be V1 and the voltage of the 2nd power terminal 2 be V2, and the relation of them be V1>V2. The output of an OR circuit comprising resistors, transistors (TRs), current sources 13, 14, 15, 16 and 17 is given to ORs 19, 20, 21, 22, 23, 24 by using level shift circuits 12, 10, 9, 8. A base potential of a TR 21, that is, a DC potential V11 of an output terminal 11 of a level shift circuit is not necessarily kept constant at all times, but the voltage V2-V11 should always be a value not saturating the TR 21 against the independent variation in the voltages V1, V2. The difference between the power voltage receiving the signal to be sent and the DC potential at the output terminal of the level shift circuit depends only on the resistor and the DC level is managed without causing any hindrance onto the ECL circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a level shift circuit for a semiconductor integrated circuit that requires two or more different external power supply systems.

[Conventional technology]

Some semiconductor integrated circuits require different power supplies. In these integrated circuits, when transmitting a signal from a circuit network operating on one power supply system to a circuit network operating on another power supply system with a lower power supply, the DC component superimposed on the signal is transmitted without any inconvenience. In order to transmit signals, a level shift circuit was installed, or in order to interrupt the direct current component itself, a method was often used in which a capacitor was used to transmit only the alternating current component. As a level shift circuit, a combination of an emitter follower, a diode, and a resistor is commonly used.

[Problem that the invention seeks to solve]

However, in a conventional circuit that combines an emitter follower with a diode or a resistor, the operable power supply voltage range may be significantly narrowed depending on which power supply system generates the bias for the emitter follower's constant current source. Let's now assume that signals are received and passed between the first and second power supply systems, which are each operating independently in the first and second power supply systems, which are lower than the first power supply system. One of the first and second power supplies does not necessarily follow the other and fluctuate at the same rate, and it is extremely rare for the ripples included in the power supplies to have exactly the same phase. If a level shift circuit is configured with a bias source created in the first power supply system, even if the drift in the level shift circuit's DC potential due to ripples and fluctuations included in the first power supply circuit can be absorbed, the Second, it is impossible to prevent the effects of power fluctuations.

In particular, in ECL circuits, the output DC potential of the level shift circuit is equal to the base potential of the transistor at the signal receiver, and the receiver is always between the power supply voltage of the circuit at hand and the base potential so that the transistor does not saturate. If a conventional level shift circuit is used in a figcL circuit in which it is necessary to maintain a potential difference, the base-collector voltage of the transistor changes due to fluctuations in the '4 sources that occur independently, resulting in disadvantages such as deterioration of operating speed and saturation.

[Means for solving problems]

The level shift circuit of the present invention includes a current source that detects a potential difference between different power supplies and whose current increases or decreases depending on the voltage difference, and an emitter follower that is connected to the above-mentioned current source via a resistor. ing.

〔Example〕

FIG. 1 shows an embodiment of Akira Motobu. This embodiment is a level shift circuit that connects gCL circuits having different power supply voltages in a DC manner. 1 is the first power supply terminal and the voltage value is Vl
, 2 is the second power supply terminal and the voltage is v2 [Vx)Vs
shall be. In the circuit shown in Fig. 1, the output of the OR consisting of resistors, transistors, and current sources 13, 14, 15, and 16°17 is 1.
1 using a level shift circuit consisting of 2.10 and 9.8.
9, 20.21° 22.23.24. Although the base potential of the transistor 21 and the DC potential v11 of the output terminal 11 of the level shift circuit do not always need to be kept constant, the value of V2-Vll will vary depending on the You must always ensure a value that does not saturate. The value of Vll is the formula ■
is given by The value of 13 is 几tn, the current value of 17 is 2φI
E, the values of resistors 5, 7, 8.10, R',
R,? , R8, RIO, Vt-Vx = ΔV, ・・・・・・・・・■ Therefore, the potential difference between the potential of terminal 11 and the power supply 2 is calculated from the formula (■).As is clear from the present invention, It can be seen that in the level shift circuit consisting of the following, the difference between the power supply voltage at which the signal to be transmitted is received and the DC potential at the output end of the level shift circuit is determined only by the resistance. It is easy to make the value of equation (2) zero in circuit design, and the DC level in signal transmission between different power supply systems can be managed without interfering with the operation of the ECL circuit.

〔Effect of the invention〕

As explained above, in proportion to the voltage difference between different power supply systems,
By increasing or decreasing the current in the emitter follower's current source used for level shifting, the voltage drop across the resistor connected in series with the emitter follower's current source can be changed in accordance with the potential difference between the two power supplies. The effect is that level shifting can be carried out manually without pushing the operating point of a circuit operating on a low power supply system into a region where it saturates or degrades speed. The present invention also provides transistor PNP, N
Regardless of PN, it can be implemented.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. 1...First power supply terminal, 2...Second power supply terminal, 3.4...Transistor forming a pair of current mirrors, 5...First power supply terminal. Resistor that determines the current value of the first pair of current mirrors, 6.9... Transistors forming the second pair of current mirrors, 7, 8...
・Resistor 1 that determines the current ratio of the second pair of current mirrors
0... Level shift resistor, 11...
Output terminal of the level shift circuit, 12...Transistor constituting an emitter follower of the level shift circuit;
13, 14...Resistance forming the OR circuit/circuit,
15, 16...Transistors forming a 0 circuit,
17... Constant current source of OR circuit, 18...
・The human input signal of the OR circuit, 19.20... The signal is received by the hand, the resistance of the OR circuit, 21, 22...
The signal is received by the OR circuit transistor, 23...
... Constant current source, 24 ... Base bias power supply, 25 ... Ground point.

Claims (1)

[Claims] In a level shift circuit using an emitter follower that directly transmits a signal from a circuit operating on a first power supply system to a circuit operating on a second power supply whose absolute value is lower than that of the first power supply system, The level has a current source that detects a difference in two power supply voltages and whose current increases or decreases in the same way as the voltage difference increases or decreases, and the current source is connected in series to the emitter current path of the emitter follower via a resistor. shift circuit.