JPS62113480A - Level shifting circuit - Google Patents

Abstract

PURPOSE:To convert an external input signal into an internal signal level extending over ultra high frequency from DCs stably by providing a transfer gate, a diode clipping circuit, which is cascade-connected to the transfer gate and adjusts signal amplitude, and a level shifting circuit to the diode clipping circuit. CONSTITUTION:A level shifting circuit for converting inputs to TTL/BFL for a GaAs integrated circuit is shown in the figure. A transfer gate 4 limiting currents, a diode clipping circuit 5 limiting amplitude and a level shifting circuit 6 bringing a level to BFL are provided. Since a gate for the transfer gate 4 is connected previously to a point (b) in the figure, it functions as a constant current source, and serves as the controlling of inflow currents from the outside. Since the transfer gate 4 and the diode clipping circuit 5 are formed, external fluctuation is absorbed and signals at a TTL level can be converted stably into a BFL level up to ultra high frequency from DCs. No capacitor is required, thus miniaturizing the whole circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION A field of industrial application concerns level conversion circuits utilized in GaAS integrated circuits used as ultra-high speed digital integrated circuits.

BACKGROUND OF THE INVENTION In recent years, the demand for high-speed data processing has increased, and GaAs integrated circuits are considered to be the most promising candidate, and research is being actively carried out.

Hereinafter, a conventional level conversion circuit used in the above-mentioned GaAs integrated circuit will be explained with reference to the drawings.

FIG. 2 shows a level conversion circuit at the input section of a conventional GaAs integrated circuit. In FIG. 2, 1 is a buffer circuit, 2 is a level shift circuit, and 3 is a coupling capacitor.

The operation of the human-powered level conversion circuit configured as described above will be described below.

First, an input signal from the outside passes through the coupling capacitor 3, and its AC component is transmitted to point a. The -58 point is biased to the required C level inside the integrated circuit by the buffer circuit 1 and the level shift circuit 2. In this way, at point a, the AC component of the external signal and the C component necessary for the internal circuit are superimposed, and the external signal is converted to a predetermined signal level.

Problems to be Solved by the Invention However, in the conventional configuration as described above, since a condensing coupling is used, for example, the input signal is
There was a problem that when the same value continued like O, the operation became unstable. Another disadvantage is that the capacitor occupies a large area in the integrated circuit.

In view of the above problems, the present invention provides a level conversion circuit that can operate stably from DC to ultra-high frequencies.

Means for Solving the Problems In order to solve the above problems, the level conversion circuit of the present invention includes a transfer gate that receives an external input signal and controls the inflow current thereof, and a transfer gate that is connected in cascade to the transfer gate. This configuration includes a diode clip circuit that adjusts the signal amplitude by adjusting the signal amplitude, and a level shift circuit that is further connected to the diode clip circuit and adjusts the signal to a predetermined level.

According to this configuration, the input signal is passed through the transfer gate to a current of 1t, and the amplitude is controlled by the diode clip circuit.This amplitude control improves the logic operation speed and also increases the speed of transmission to the internal circuit. signal amplitude is stabilized. Further, since the inflow current is controlled to be constant by the transfer gate, the clip voltage by the diode clip circuit is controlled extremely stably. Further, the input signal whose waveform has been stably shaped as described above is level-shifted to a required level by a level shift circuit. Moreover, since a capacitor unlike the conventional one is not required, the entire circuit can be miniaturized.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a level conversion circuit for TTL/BFL input conversion of a GaAS integrated circuit in one embodiment of the present invention. In FIG. 1, 4 is a transfer gate that limits current, 5 is a diode clip circuit that limits amplitude, and 6 is a level shift circuit that changes the level to BFL, and these are connected in cascade in this order.

The operation of the level conversion circuit for TTL/BFL input conversion configured as described above will be described below. First, a TTL level signal input from the outside passes through the transfer gate 4. Since the gate of this transfer gate 4 is connected to point b in FIG. 1, it functions as a constant current source and has the effect of controlling the inflow current from the outside. The diode clip circuit 5 connected to this transfer gate 4 reduces the amplitude to about 1.5V and makes the logic 1! l! This is to improve the operating speed and to stabilize the amplitude transmitted to the internal circuit. In addition,
This clip voltage has the feature that it is controlled extremely stably because the inflow current is controlled to be constant by the action of the transformer 7 and the gate 4.

The above was the operation when the input signal was High, but when it is Low
When transitioning to w, point b becomes the drain of the transfer gate 4, so its conductance becomes very large and the falling speed of the signal becomes extremely fast. The level shift circuit 6 converts the input signal shaped as described above into B F
It is for level shifting to the L level (-0.5V to -2.OV), and also has a 1m buffer capacity.

As described above, according to this embodiment, by providing the transfer gate 4 and the diode clip circuit 5,
It is possible to absorb external fluctuations and convert TTL level (A) to BFL level extremely stably from direct current to ultra-high frequency. Also, because it does not require a capacitor like conventional ones, the entire circuit can be made smaller. be able to.

Effects of the Invention As described above, the present invention converts external input 〇 extremely stably from direct current to internal No. 18 level over ultra-high frequencies by cascading a transfer gate, a diode clip circuit, and a level shift circuit. It can be done, and its practical effects are great.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a level conversion circuit according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a conventional level conversion circuit. 4...Transfer gate, 5...Diode clip circuit, 6...Level shift circuit Representative Yoshihiro MorimotoFigure 1Figure 2!

Claims (1)

[Claims] 1. A transfer gate that receives an input signal from the outside and controls its inflow current, a diode clip circuit that is cascade-connected to this transfer gate to adjust the signal amplitude, and a diode clip circuit that is further cascade-connected to this diode clip circuit to adjust the signal. A level conversion circuit comprising: a level shift circuit for adjusting to a predetermined level.