JPS5914855Y2 - Exponential waveform generation circuit - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a signal generation circuit that generates an exponential waveform.

Conventional exponential function waveform generation circuits include, for example, as shown in FIG. 1, a circuit that applies a ramp voltage 2 to an antilogarithmic amplifier 1 to obtain an exponential function waveform 3, and as shown in FIG.
A device is known in which an exponential function waveform 6 is obtained by applying a ramp voltage 5 to a multiplier 4.

However, such a conventional exponential function generating circuit has a drawback that the circuit configuration is complicated.

This invention was made in order to eliminate such conventional drawbacks, and the purpose is to provide a circuit that has a simple configuration and generates an exponential waveform with high accuracy.

To distantly relate to that object, the invention comprises: (a) a voltage source; (b) a first transistor whose emitter is connected to said voltage source via a first resistor; and whose emitter is connected to a second resistor. and a second transistor whose base is connected to the collector and the base of the first topsisistor, and outputs two currents separately from the collectors of the first and second transistors. (C) a third transistor whose base and collector are connected to the collector of the first transistor; (d) a capacitor interposed between the emitter of the third transistor and a reference potential point; (e) a switch connected in parallel to the capacitor; (f) a fourth transistor having a base connected to the base of the third transistor and a collector connected to the collector of the second transistor; (g) a third resistor inserted between the emitter of the fourth transistor and the reference potential point; and (h) a fourth resistor inserted between the collector of the fourth transistor and the reference potential point. It has a similar structure.

Embodiments of this invention will be described below with reference to the accompanying drawings.

FIG. 3 shows an embodiment of this invention.

In this embodiment, the voltage source 11 (10 VER) applies a constant positive voltage to the current generating section 12.

The current generating section 12 includes a first resistor 13 and a second resistor 15 connected in series to the voltage source 11 and in a parallel relationship with each other.
, a first transistor 14 whose emitter 14e (input end) is connected to the first resistor 13, and a first transistor 14 whose emitter 16e (input end) is connected to the second resistor 15, whose base 16b (control input end) and collector 16C ( a second transistor 16 whose output end) is connected to the base 14b (control input end) of the first transistor; A current is output that is inversely proportional to the value of the resistor 13.15.

That is, the value of the first resistor 13 is changed to aR1, the value of the second resistor 15
If the value of is R and the current output from the collector 14C of the transistor 14 is i (t), the current output from the collector 16C of the second transistor 16 is a, 1(
t).

The collector 14C of the first transistor 14 is connected to the collector 17C (input end) of the third transistor 17, and the collector 17C and base 17b of the third transistor 17 are connected to each other.
(control input terminal) are commonly connected, and the third transistor 17
A capacitor 18 is connected between the emitter 17e (output end) and the ground point, and a switch 19 is connected in parallel to the capacitor 18.

The collector 16C (output end) of the second transistor 16 is connected to the collector 20C (input end) of the fourth transistor 20, and the base 20b (control input end) of the fourth transistor 20 is connected to the base 17b of the third transistor 17. and the emitter 20e (output end) of the fourth transistor 20
A third resistor 21 is connected between the collector 16C of the second transistor 16 and the ground, and a fourth resistor 22 is connected between the collector 16C of the second transistor 16 and the ground. is the output terminal 23 of this entire circuit.

Note that the first and second transistors 14 and 16 are PNP transistors, and the third and fourth transistors 17°20
is an NPN) transistor.

Next, the operation of the embodiment configured as described above will be explained.

Now, when the switch 19 is open, a current i (t) flows from the voltage source 11 to the capacitor 18 via the first resistor 13, the first transistor 14, and the third transistor 17.
flows, and if the capacitance of the capacitor 18 is C, then the voltage Vc across the capacitor 18 is expressed as follows.

On the other hand, the voltage source 11 is connected to the third resistor 21 via the second resistor 15, the second transistor 16, and the fourth transistor 20.
When the value of the third resistor 21 is RE, and the current amplification factor of the fourth transistor 20 is β, the current at 1(t) flowing in is as follows.

Therefore, Then, becomes.

here, Then, becomes.

If the initial charge charged in the capacitor 18 is QO, then i (t)=KQoekt...-(7) Therefore, the voltage across the resistor 21, that is, the output voltage V.

is Vo=REai (t)=KRFlQoekt---
-...(8) Therefore, since there is the relationship voOcekl...(9), the output voltage has an exponential function waveform as shown in FIG.

When the switch 19 is closed, the charge on the capacitor 18 is discharged through the switch 19, and when the voltage across the capacitor 18 becomes O, the emitter 1 of the third transistor 17
7 e becomes the ground potential, the base of the fourth transistor 20 also becomes a potential close to the ground potential, and the fourth transistor 2
0 is the off state.

As a result, the collector 16 C of the second transistor 16
The current outputted from the fourth transistor 20 flows to the ground point through the fourth resistor 22, and the potential of the emitter 20e of the fourth transistor 20 also becomes the ground potential.

Then, when the switch 19 is opened again, an exponential function waveform is obtained.

Note that the waveform change can be made faster or slower by changing the ratio of the values of the first and second resistors 13.15.

Note that the embodiment described above is one aspect of this invention, and can be modified in various ways.

For example, in the embodiment shown in FIG. 3, the collector 17C and base 17b of the third transistor 17 are commonly connected, the collector 17C is connected to the collector 14C of the first transistor 14, and the emitter 17e is connected to the capacitor 18. ,
The base 17b is connected to the base of the fourth transistor 20, but instead of this configuration, the anode of the diode is connected to the collector 14C of the first transistor 14 and the base 20b of the fourth transistor 20, and the cathode may be connected to the capacitor 18.

The same applies to the second transistor 18.

That is, since the second and third transistors are diode-connected, the same effect can be obtained even if each is replaced with a diode.

In the embodiment shown in FIG. 3, the first and second transistors 1
4.16 is PNP type, 3rd and 4th transistor is NPN
However, by making the polarity of the voltage source 11 negative, the first and second transistors 14 and 16 can be configured as NPN type, and the third and fourth transistors can be configured as PNP type.

Further, the exponential function waveform generating circuit according to this invention is not limited to PN junction transistors, but can also be constructed using field effect transistors, vacuum tubes, etc. In short, the above-mentioned first, second, third, and fourth transistors It can be constructed by providing a two-terminal or three-terminal switching element corresponding to 18.20.

Further, if the switch 19 is automatically opened and closed at regular intervals, an exponential sweep waveform can be obtained.

As is clear from the above explanation, according to this invention, 4
An exponential function waveform can be easily obtained by using only one switching element and a few passive elements, and it can be used in many ways, such as as a sweep oscillator.

[Brief explanation of the drawing]

1 and 2 are block diagrams showing a conventional example, FIG. 3 is a circuit diagram showing an embodiment of this invention, and FIG. 4 is a waveform diagram showing an example of waveforms obtained by the circuit of FIG. 3. . 11... Voltage source, 12... Current generating section, 13... First resistor, 14... First
Transistor, 15...Second resistor, 16...
...Second transistor, 17...Third transistor, 18...Capacitor, 19...
...Switch, 20...Fourth transistor, 2
1...Third resistor, 22...Fourth resistor.

Claims (1)

[Scope of Claim for Utility Model Registration] An exponential function waveform generating circuit that has the following (A x beauty in the mouth≠1X-X)) (A). (a) Voltage source. (b) a first transistor whose emitter is connected to the voltage source via a first resistor; whose emitter is connected to the voltage source via a second resistor; whose base is the collector and the base of the first transistor; a second transistor connected to the current generator, and outputs two currents separately from the collectors of the first and second transistors. (c) A third transistor whose base and collector are connected to the collector of the first transistor. B) A capacitor interposed between the emitter of the third transistor and a reference potential point. (E) A switch connected in parallel to the capacitor. (f) The base is the third. a fourth transistor connected to the base of the transistor and having a collector connected to the collector of the second transistor; (g) A third resistor interposed between the emitter of the fourth transistor and a reference potential point. D) A fourth resistor interposed between the collector of the fourth transistor and a reference potential point.