JPS5916651B2 - time constant circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a time constant circuit, and is primarily directed to a time constant circuit used in a measuring device 2.

In the semiconductor industry, photoetching technology is indispensable for fine d--7J loe of semiconductor substrates and their surface coating materials.

This photoetching technique involves coating the surface of the workpiece with a photosensitive corrosion-resistant coating called photoresist, irradiating it with light through a mask (photomask), and partially photopolymerizing the photoresist due to the shadows. This is a technique in which a photoresist mask corresponding to the mask is formed by processing, and a part of the workpiece is etched using the photoresist mask. By the way, in order to produce the photomask mentioned above, a first image that is reduced to one-twentieth the original size, for example, 200 times the actual size, is used.
A glass master plate is made, then further reduced to one-tenth of its original size, and this master mask (positive image) is used as a master mask (positive image), from which five working masks (negative images) are printed.

This working mask is brought into close contact with a photoresist film as a photomask, and about 20 sheets can be printed with one mask. A working mask, ie, a dry plate, is produced from the master mask by irradiating light from a mercury lamp or the like from the upper surface of the master mask and exposing the dry plate to the transmitted light.

In this method, for mass production, it is necessary that the amount of light at the dry plate section be constant, and various devices have been considered for measuring the amount of light. FIG. 5 is a circuit diagram showing an example of a digital light meter that can be considered as the light amount measuring device.

As shown in the figure, it consists of a solar cell 1, an amplifier 2, a time constant circuit (smoothing circuit) 3, and a digital panel 4.
Detecting light with the solar cell 1 and converting it into electric current,
This is converted into a voltage by amplifier 2, and the output vln
is applied to the digital panel 4 via the time constant circuit 3,
It performs digital display. 5. By the way, when a mercury lamp is used as a light source as described above, its discharge characteristics are unstable, so flickering occurs and there are generally small fluctuations.

The above-mentioned time constant circuit smoothes the above-mentioned small fluctuations and produces a stable output V. Since it is used to apply u4 to a digital panel to provide an accurate display that is easy to read (flicker-free), it is necessary that its time constant be large. However, if the time constant is set to a large value, the followability of the output to large voltage changes will deteriorate.
This has the problem that the measurement time becomes longer.

FIG. 6 shows the input voltage Vin and output voltage V of the time constant circuit for explaining the above problem. FIG. 2 is a voltage waveform diagram showing the relationship between ut and ut. As shown in the figure, although small fluctuations in the input voltage Vin can be smoothed, large voltage changes (periods Tl and t2 in the figure) result in smoothing of the output voltage V. The change in ut is delayed, and as a result, rapid measurement cannot be performed. The present invention has solved the above-mentioned problems, and its purpose is to provide a time constant circuit that can smooth out small fluctuations in the input voltage and also allow the output voltage to follow large fluctuations. It is about providing. The basic configuration of the present invention for achieving the above object is as follows: at least, an impedance means and two complementary-connected unidirectional elements are connected in parallel, a capacitance means is connected in series to this parallel connection circuit, and this It is characterized in that the output is taken out from the connection point of a series-connected circuit.

The present invention will be specifically described below with reference to embodiments and drawings.

FIG. 1 is a circuit diagram showing an example of the time constant circuit of the present invention.

As shown in the figure, the resistance R.

, Npn transistor Q1 and Pnp transistor Q2
A capacitive element C is connected in parallel with a complementary circuit. are connected in series, and the output VOut is taken out from this series connection point. In addition, the transistor Q
Npn transistor Q1 to supply current to l, Q2
The collector of Q2 is connected to the positive power supply (+V) terminal via resistor R1, and the collector of Pnp transistor Q2 is connected to resistor R2.
Connect the emitters of both transistors to the negative power supply (-V) terminal through the capacitive element C. Connect to the charge/discharge side terminal of the Also, the values of resistors R1 and R2 are resistors R. (In extreme cases, it may not be necessary). By varying the resistance values in this way, a circuit with a large time constant (RO-CO) and a circuit with a small time constant (R
1・CO), (R2・CO), and in the present invention, a circuit with a small time constant is used for large changes in the input voltage Vin, and a circuit with a small time constant is used for large changes in the input voltage Vin. The aim is to achieve the objective by using different circuits with large time constants. FIG. 2 shows the input voltage ViO and output voltage V for explaining the operation of the time constant circuit. FIG. 2 is a voltage waveform diagram showing the relationship between ut and ut. As shown in the figure, when the input voltage ViO increases linearly from 0V to a high voltage (
During the period TO-t1), the input voltage Vin and the capacitive element C respond to such a large voltage change.

When the difference between the terminal voltage (VOul) of the transistor Q1 exceeds the operating voltage (VBE) of the transistor Q1,
1 turns on, resistor R1 and capacitive element C. Because the power supply voltage (+V) is quickly photovoltaic by a small time constant circuit, the output voltage V. ul changes following the input voltage ViO. Next, when the input voltage Vin varies finely with respect to a certain voltage (period t1 to T
2) includes the input voltage In and the output voltage V.

The potential difference with Ol is the operating voltage (VBE
), this transistor is turned off, and the input voltage is the resistance current and capacitance element C. The output voltage through a circuit with a large time constant consisting of and. It is retrieved as u1. Therefore, the input voltage VlO is smoothed. Furthermore, the input voltage ViO starts to drop rapidly, and the output voltage V
.

The potential difference with Ol is the operating voltage of the Pnp transistor Q2 (
VBE) (period T3), this transistor Q
2 is turned on, thus resistor R2 and capacitive element C. A circuit with a small time constant consisting of a circuit with a small time constant discharges quickly, thus reducing the output voltage V. ul changes following the input voltage Vin. In addition, when a small fluctuation occurs at a certain potential (period T3 to T4), the input voltage Vi
n and output voltage V. Since the potential difference with ut becomes less than the operating voltage (VBE) of transistor Q2, this transistor is turned off and the input voltage is applied to resistor R. and capacitive element C. The output voltage V through a circuit with a large time constant consisting of.
It will be taken out as Ol, and the voltage will be smoothed. As described above, the present invention (1) extracts the output voltage by switching between a circuit with a small time constant for large voltage changes and a circuit with a large time constant for small fluctuations. This provides a time constant circuit that can smooth small fluctuations in input voltage and follow large voltage changes.

Since it is a time constant circuit having such a function, it becomes an optimal time constant circuit for the above-mentioned digital light meter and the like.

The present invention is not limited to the above embodiments, and various modifications can be made.

For example, in the above embodiment, complementary connected bipolar transistors are used as switching means for circuits having different time constants, but the invention is not limited to this, and a similar configuration may be provided by complementary connected insulated gate field effect transistors FET. ,
Other amplification elements may also be used.

Further, based on the same concept, two diodes Dl and D2 having an operating voltage VF may be connected complementary to each other as shown in FIG. 3.

In such a case, there is an advantage that there is no need to separately provide a power supply terminal. Furthermore, as shown in FIG. 4, a diode D3 is connected to the base side of the transistor Q1 and a transistor Q2
The configuration may be such that a diode D4 is additionally connected to the base side of the .

In such a case, the diodes D3 and D4 are used for level shifting, and the voltage for operating the transistors Ql and Q2 becomes high (BE+F). Therefore, there is an advantage that even if the fluctuation width of a small fluctuation in the input voltage In becomes large, it can be smoothed. To play a similar role,
It goes without saying that Zener diodes may be used for level shifting instead of the diodes D3 and D4. The present invention can be widely used as a time constant circuit.

[Brief explanation of the drawing]

FIG. 1 (3) is a circuit diagram showing an example of the time constant circuit of the present invention; FIG. 2 is a voltage waveform diagram for explaining its operation; FIGS. 3 and 4 are circuit diagrams showing other examples; The figure is a circuit diagram showing an example of a digital light meter, and Fig. 6 is a voltage waveform diagram for explaining the operation of the time constant circuit therein. 1...Solar cell, 2...・Amplifier, 3・
...Time constant circuit, 4...Digital panel, RO, Rl~R3...Resistor, Ql, Q2...
...Transistor, D1-D4...Diode, CO...Capacitive element.

Claims (1)

[Claims] 1. A time constant circuit characterized in that at least an impedance means and a unidirectional element are connected in parallel, a capacitance means is connected in series to this parallel connection circuit, and an output is taken out from a connection point of this series connection circuit.