JPS60117903A - Level shift circuit - Google Patents

Abstract

PURPOSE:To constitute easily a level shift circuit which converts the DC bias voltage into an optional level by using a semiconductor IC and adding a small number of resistances of small resistance value and a buffer amplifier. CONSTITUTION:A voltage attenuation circuit 10 consists of a ladder resistance circuit 11 and a buffer amplifier 12. Both the number of stages of ladder resistances and the combinations of resistance values forming said ladder resistances can be set optionally in order to obtain a desired attenuation factor. In this case, no current flows to a resistance 9 and the circuit 11 when the input signal impressed to a terminal 1 has the DC voltage since the circuit 11 is set between a signal output/input terminal 5 and a bias voltage source 8. Therefore the voltage of the terminal 5 is coincident with the source 8. In other words, the DC bias voltage value of the output voltage can be set optionally by the voltage of the source 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a level shift circuit that converts a value into a desired value, and provides a level shift circuit particularly suitable for semiconductor integrated circuit implementation.

[Background of the invention]

In order to match the operating level of the signal processing circuit with the input signal level, it is possible to control the operating level of the signal processing circuit, but for example, in semi-dynamic integrated circuits, the operating level of the signal processing circuit is fixed. In this case, it is necessary to change the input signal level using a level shift circuit.

Various types of level shift circuits, especially level shift circuits for analog signals, are known, but the ones that have low distortion and are easy to make using semiconductor wave generation technology are the arithmetic amplifiers, capacitors, and resistors shown in Figure 1. Level shift circuits made up of elements are known.

The input signal via the input terminal 1 and the capacitor 6 and the bias voltage from the bias power supply 8 are applied to the negative phase and positive phase input terminals of the operational amplifier, respectively. A part of the calculation output is applied to the negative phase input terminal via the capacitor 7. In principle, with the above configuration, it is possible to obtain a level-shifted signal that is in reverse phase with the input signal and has a bias voltage that matches the voltage of the power supply 8, but in practice, in order to stabilize the operation of the amplifier 2, feedback is required. Resistor 9 is absolutely essential. However, in this case, the charge in the capacitor 7 is discharged by the resistor 9, so when handling low frequency components as an applied voltage signal, the capacitance value of the capacitor 6.7 and the resistance value of the resistor 9 must be extremely large. Therefore, it is impossible to realize a level shifter in a semiconductor integrated circuit that is intended to be economical.

[Purpose of the invention]

Therefore, an object of the present invention is to realize a level shift circuit that can be realized with a semiconductor integrated circuit, and more specifically, in a level shift circuit as shown in FIG. First, the circuit is configured so that the resistance value against discharge operates as an equivalently large resistance value.

[Summary of the invention]

In order to achieve the above object, the present invention has the following features as shown in FIG.
A voltage attenuation circuit 10 is added in series with the feedback resistor 9 and connected in parallel to the feedback capacitor 7. With this configuration, the equivalent feedback resistance value can be doubled as the value of the resistor 9 by causing the voltage attenuation circuit to output 1/2 times the output signal amplitude (K is an arbitrary number). That is, the first
Although the resistance value of the resistor 9 shown in the figure is small, it can be operated as an equivalently large resistor.

[Embodiments of the invention]

Hereinafter, the configuration and operation of the present invention will be explained in detail using examples.

FIG. 3 shows a circuit diagram of an embodiment of a level shift circuit according to the present invention.

In the figure, a voltage attenuation circuit 10 is composed of a ladder resistor 11 and a buffer amplifier 12, and the number of stages of the ladder resistor and the combination of the resistance values composing them are arbitrarily determined so as to obtain a desired attenuation factor. Can be set. In this case, since the ladder resistance circuit 11 is installed between the signal output terminal 5 and the bias voltage source 8, when the input signal applied to the terminal 1 is a DC voltage, the resistance 9 and the ladder resistance circuit are No current flows and therefore the voltage at terminal 5 is biased from bias power supply 8.
Matches the voltage of That is, in other words, the DC bias voltage value of the output voltage can be arbitrarily set using the voltages of 8.

Next, the alternating current voltage component of the human power signal causes an alternating current to be generated in the capacitor 6, so that the current is shunted to the resistor 9 and the capacitor, and the output voltage accordingly changes.

Now, since voltages corresponding to the capacitance values of the capacitors 6 and 7 are applied to the bulk resistor 9, there is a voltage between the input AC voltage i and the output AC voltage V, which represents the operation of the circuit of this embodiment. The following formula holds true.

i.e. However, S is a Laplace variable.

Therefore, - for example, if the cutoff frequency is set to IH2,
In other words, if we set the resistance value condition such that frequency components higher than IH2 are output, -2πC2K holds true, so here c2=109F', and =10'
If you choose , R will be approximately 16Ω. In this case -10
' is, for example, IOKΩ and 0. This can be realized by using resistors of I KΩ in a three-stage ladder configuration as shown in FIG.

In contrast to this embodiment, in the conventional example shown in FIG.
It turns out that it is completely unsuitable for semiconductor integration.

〔Effect of the invention〕

As explained above, according to the present invention, a level shift circuit that converts a DC bias voltage to an arbitrary value can be easily and easily created using a semiconductor integrated circuit by simply adding a small number of resistors with small resistance values and one buffer amplifier. It is economically feasible.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional example, FIG. 2 is an original circuit diagram of the present invention, and FIG. 3 is a circuit diagram of an embodiment of the present invention.

Claims (1)

[Claims] A DC bias potential is applied to the positive phase input terminal of the operational amplification stage, a first capacitor is connected between the negative phase input terminal and the signal input terminal of the amplifier, and a first capacitor is connected between the negative phase input terminal and the output terminal of the amplifier. Second
In the amplifier circuit connected to the capacitor, an attenuation circuit that generates a divided voltage of the output signal amplitude of the operational amplifier and a resistor connected in series with the attenuation circuit are connected in parallel to the second capacitor. level shift circuit.