JPS62122294A - Signal processor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field] The present invention is suitable for application to high frequency circuits or cases where signal transmission is performed from a first semiconductor integrated circuit to a second semiconductor integrated circuit (hereinafter referred to as an IC). The present invention relates to a signal processing circuit.

[Background technology]

Between each lead of an IC, between each pad of an IC chip, and between each circuit pattern of a printed circuit board.

A resistor, capacitor, and coil are formed. These are undesirable because they constitute unnecessary distributed constant circuits and contribute to deterioration of single frequency characteristics and reduction in crosstalk.

According to studies conducted by the inventors of the present invention, it has become clear that when a transmission signal is transmitted by a voltage change, charging and discharging occur in the capacitor, thereby causing the above-mentioned undesirable phenomenon.

Therefore, by reducing the capacitor component, deterioration of frequency characteristics, reduction in crosstalk, etc. can be reduced.

For this reason, various efforts have been made regarding the positions of pads on IC chips, etc., and capacitor components have been reduced.

However, for IC users, the circuit length may become longer due to restrictions during mounting. in this case,
It was discovered that a capacitor component unexpected by the IC manufacturer was formed and that initial circuit operation could not be obtained due to this.

Therefore, the inventor of the present invention realized that the above-mentioned undesirable phenomenon can be significantly reduced if signal transmission is performed without being affected by the capacitor component, and came to propose the present invention.

Furthermore, in "Design of High Frequency Circuits" (November 25, 1975, 7th Edition, Issue 1, Publisher: CQ Publishing, p. 137), there is a statement that it is desirable to keep lead wires as short as possible, especially in the high frequency range. There is.

[Purpose of the invention]

An object of the present invention is to provide a signal processing circuit that can perform good signal transmission regardless of the presence or absence of a capacitor component in a signal transmission path.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[Summary of the invention]

A brief summary of typical inventions disclosed in this application is as follows.

That is, the signal transmitted from the output circuit with high output impedance to the input circuit with low input impedance causes ti
Provides a controlled amount of output current. The capacitor component of the transmission path is initially charged and does not discharge in response to changes in the output current, and signal transmission can be performed virtually ignoring the capacitor component, regardless of the presence or absence of the capacitor component. Therefore, the object of the present invention, which is to perform good signal transmission, can be achieved.

[Embodiment 1] Hereinafter, a first embodiment of a signal processing circuit to which the present invention is applied will be described with reference to FIGS. 1 and 2. Note that FIG. 1 shows a circuit diagram of the main parts of a VTR to which the present invention is applied, and FIG. 2 is a plan view showing an example of the arrangement of ICs mounted on a printed circuit board.

The feature of this embodiment is that it is configured to facilitate signal transmission between two ICs used in a VTR.

1 is a magnetic tape, and 2 is a reproducing head.

The reproduction signal Va is supplied to the reproduction amplifier 3 via the No. 1 terminal.

4 indicates a luminance signal processing system, and 5 indicates a color signal processing system. The luminance signal Y and color signal C are sent to a mixing circuit 6.
supplied to A composite video signal vb in which both are mixed is obtained from the mixing circuit 6.

Although the composite video signal vb is a high frequency signal, it is transmitted smoothly from the IC to the IC2 by the circuit operation of the signal processing circuit 110 to which the present invention is applied.

That is, the signal processing circuit 11 includes an output circuit 11a and an input circuit 11b as used in the present invention.

Transistors Ql, Q, and resistors R, , R, constitute a current mirror circuit, and the reference current Ia flowing through transistor QI is controlled by transistor Q, which performs voltage-'ME current conversion. Note that the resistor R3 is the voltage of the base S current 1a.
, define the amount.

When the reference current Ia is controlled by the composite video signal vbK, the output chamber iIb also changes corresponding to the reference II current Ia.

Here, when looking in the direction of the transistor line 2 from the No. 3 terminal, there is a high resistance between the collector and emitter of the transistor Q2, and this becomes the output current/pedance of the output circuit 11a.

On the other hand, regarding the input circuit 11b, the transistor Q
The emitter voltage Ve of No. 4 is Vref −VbeQ.

determined by Note that Vref is the voltage level of the base '1!1 voltage, and VbeQ4 is the voltage level of the transistor Q
This is the base-emitter voltage of 4.

Emitter voltage ve is output 1! It does not change due to ff1Ib and maintains a nearly constant voltage level -I
The input impedance seen from the first terminal of Ct is a low impedance and does not change.

Then, the change in the output current Ib is converted into a current-voltage by the load resistor R1, and an output signal Vo corresponding to the level change of the one composite video signal vb is obtained.

What should be noted here is whether or not there is a signal change in the line 1a, which is the signal transmission path.

As shown in the above circuit operation, the voltage level of the line 1a is fixed at the voltage LEVe, and there is no change in the voltage level.

The signal is transmitted from the output chamber IIb to the IC2.
This is done by changing the current. Therefore.

Even if a capacitor component is present in the line 1a as shown in the figure, this capacitor C does not perform charge/discharge operations and does not affect signal transmission1. Therefore, due to mounting constraints, IC + and IC2 are arranged on the printed circuit board 12 as shown in FIG. 2, and even if the line la becomes long, the influence of the capacitor C is reduced, so that good signal transmission can be achieved.

Therefore, the degree of freedom in design during mounting is improved, and in particular, the design of high frequency circuits is facilitated.

Note that 13 is an amplifier, and a video signal amplified to a predetermined voltage level is supplied to the television receiver 14 via a No. 3 terminal.

[Embodiment 2] Next, a second embodiment of the present invention will be described with reference to FIG.

Note that FIG. 3 is a circuit diagram of the signal processing circuit.

It is assumed that this is applied to a VTR. The same parts as in the first embodiment are given the same reference numerals to avoid duplication of explanation.

The feature of this embodiment is that current mirror circuits are used for the output circuit and the input circuit.

The transistor QllIQ+2 and the resistor R11+Rtt constitute a current mirror circuit, and the reference current Ia is controlled by the transistor QI3. Resistor R7, is.

This defines the amount of current of the basic mt flow Ia.

The output impedance of the output circuit 11a is the power supply V c
The impedance is determined by the connection with the supply circuit c, but as above, since it is an oven collector, it has a high impedance.

On the other hand, the voltage level Ve of the signal transmission pin la is determined as follows.

That is, in the input circuit 11b, the transistor Q + Q1s - the resistor R14*R1s constitute a current mirror circuit, and the diode D is provided as a level thick transistor. Resistor R14 is a small resistance, electric EEVe
is determined by vbeQ+a''VfD, where VbeQ+4 is the pace-to-emitter voltage of transistor Q+4, and VfDI is the forward voltage of diode D.

Similarly to the above, the voltage level of voltage Ve does not change depending on output current Ib. The input impedance seen from the No. 1 terminal of the IC is extremely low.

Output current Ib becomes a reference current in input circuit 11b. Then, the output current corresponding to the electric current iIb is the load resistance R
1 to obtain an output signal Vo.

As a result of the circuit operation described above, regardless of the presence or absence of the capacitor component C, signal transmission can be performed satisfactorily in the same way as described above.

〔effect〕

(1) Signal transmission is achieved by providing an output circuit with high output impedance in the first IC, providing an input circuit with low input impedance in the second IC, and driving the input circuit with the output of the output circuit. The effect is that the capacitor component interposed between the paths is not charged or discharged, and good signal transmission is performed regardless of the presence or absence of the capacitor component.

(2) Due to (1) above, restrictions such as making the circuit pattern wiring particularly short during IC mounting are reduced, so
This has the effect of increasing the degree of freedom in design.

(Since the stray capacitor component generated between the terminals of the 311C can be ignored, the design and layout of the IC itself become easier.

Although the invention made by the present inventor has been specifically explained above based on examples, it is understood that the present invention is not limited to the above-mentioned examples, and can be modified in various ways without departing from the gist of the invention. Needless to say. For example, the output circuit and the input circuit may be provided in the same IC to improve signal transmission between external connection terminals.

[Application field]

In the above explanation, the invention made by the present inventor was mainly applied to VTR, which is the background field of application, but the invention is not limited to this. It can be widely used in machines, wireless telephones, etc.

[Brief explanation of drawings]

FIG. 1 shows a circuit diagram of a signal processing circuit to which the present invention is applied. FIG. 2 shows a plan view of essential parts showing the mounting of an IC equipped with a signal processing circuit, and FIG. 3 shows a circuit diagram of a signal processing circuit showing a second embodiment of the present invention. 11... Signal processing circuit, 11a... Output circuit, ll
b...Input circuit h Q+-Q+s...Transistor, D...Diode, Ve...Voltage level, la
... Signal transmission path - I a + I b ... Current,
C... Capacitor component, Ve... Voltage level. Agent: Patent attorney Masaru Ogawa, male 4.゛・（′・′ ・ゆ／ Figure 3

Claims (1)

[Claims] 1. (1) An output circuit that derives a controlled output current with high output impedance. (2) A signal processing circuit comprising: a low input impedance input circuit to which the output current is supplied as a transmission signal; and a signal processing circuit that performs signal transmission by controlling the output current.