JPS621306A - Stc amplifier - Google Patents

Abstract

PURPOSE:To form an optional STC curve by deciding a control voltage impressed to a current control circuit or an element depending on a data in a storage device. CONSTITUTION:The desired STC curve data is stored in the storage device (ROM) A3. Then a count of a counter circuit A4 is given sequentially to the ROM A3 synchronously with a clock pulse. Then an address signal in the ROM A3 is changed one after another and the digital output from the ROM A3 is being changed one after another. As a result, an output voltage ESTC of a D/A converter A2 impressed to the current control circuit or the element A1 is changed as time and the current flowing to an amplification factor control element constituting an amplifier circuit A is changed as time. Thus, the amplification factor of the amplifier circuit A is changed with time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an STC amplifier in which the gain (or degree of amplification) of the amplifier changes over time.

[Summary of the invention]

In an STC amplifier, the present invention provides a current control circuit for an amplifier circuit that controls the current flowing through the constituent elements to change the amplification degree, or a control voltage applied to the element by determining the control voltage applied to the element based on data stored in a storage device. This not only makes it possible to correct deviations from a desired STC curve due to the characteristics of the curve, but also allows creation of an arbitrary STC curve.

[Conventional technology]

Conventionally, there is an STC amplifier as shown in FIG. In the figure, e'' is an input signal, A is an amplifier circuit whose amplification degree can be changed by controlling the current flowing through the elements (for example, transistors, etc.) that make up the amplifier circuit, and Ql is the control current flowing through the amplifier circuit A. FET-Rt, R
2 is a resistor, C is a capacitor% Q2 is a transistor, B is a constant current circuit that flows charging current I into capacitor C, R3
is a resistor for controlling the current of the constant current circuit B, and SW is a switch for discharging the charge stored in the capacitor C.

In such an STC amplifier, when the switch SW is closed, the voltage value determined by the value of the resistor R1, the voltage division ratio of the resistor R2, and the value of the negative power supply voltage -
The gate and source of x (between ■ and ■ in the figure) are reverse biased.

Charging of the capacitor C starts at the same time as the switch SW opens, and the voltage across the capacitor C gradually increases. Along with this, the reverse bias voltage value between the gate and source of FETQ1 gradually decreases with time,
The current flowing through FETQ1 increases as the voltage across capacitor C increases (.

That is, the amplification degree of the amplifier circuit A changes with time after the switch SW is opened.

[Problem that the invention seeks to solve]

However, in such a conventional STC amplifier, the reverse bias voltage value of the FET (:h) is changed depending on the charging voltage of the capacitor C, and the current flowing through the amplifier circuit A is controlled. Since the depth of the reverse bias voltage of h is determined by the voltage division ratio of resistor R2, and the charging speed of capacitor C is determined by the magnitude of the current of constant current source B, a certain similarity to the STC curve showing the relationship between time and amplification degree is achieved. In addition, if the STC curve deviates from the desired STC curve due to the characteristics of transistors, etc., which are components of the amplifier circuit for controlling the amplification degree, it is not possible to correct this.

Furthermore, when such an STC amplifier is applied to an ultrasonic level needle or an ultrasonic berthing speed needle, it is possible to create not only a fixed STC curve but also a flexible STC curve depending on the environment or surrounding conditions in which these devices are used. There are times when we want to make changes, but existing circuits cannot meet such demands.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a current control circuit for an amplifier circuit that controls the current flowing through the components of the amplifier circuit to change the degree of amplification, or a control bias of the elements. A digital-to-analog (D/A) converted digital output from a storage device storing STC curve data was applied as a voltage.

[Effect]

Since the control bias voltage is created from the output of the storage device, if the desired STC curve data is stored in the storage device in advance, the control bias voltage corresponding to the desired STC curve can be easily obtained.

〔Example〕

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

FIG. 1 is a block diagram illustrating a preferred embodiment of the present invention. In the figure, A is an amplifier circuit whose gain changes by controlling the current flowing through the component elements, A1 is a circuit or element that can control the current flowing through the amplifier circuit A by receiving a voltage that changes from the outside, and A2 is a digital input value. A3 is a read-only memory (ROM>) in which the digital value data to be applied to the D/A converter A2 is written, and A4 is a D/A converter that provides an address signal to the address input terminal of this ROM. E3 is a reset pulse for adjusting the initial state of counter circuit A4. %E2 is a gate signal pulse that determines the effective period of the STC characteristic of this STC amplifier circuit. El is for causing counter circuit A4 to perform a counting operation. A5 is the gate signal pulse E2 and clock pulse E
1 shows an AND circuit for applying a necessary period or number of pulses E4 to a counter circuit A4 by performing an AND of 1.

FIG. 2 is a waveform diagram showing the operation timing of the above embodiment. In the same figure, El, E2, and E3 are the clock pulse, gate signal pulse, and reset pulse shown in FIG. 6BBTC, which is the input clock pulse signal of A4, is the ROM
Digital output data from A3 is sent to D/A converter A2
This shows an example of an analog voltage waveform obtained as a result of conversion into an analog voltage. ROM A3 has
Digital value data corresponding to such a voltage waveform is written.

In FIG. 1, the initial state of the counter circuit A4 is adjusted by the reset pulse E3, and at the same time, as shown in FIG. 2, an initial value of the analog voltage is given based on the first data of the ROM A3. At this time, AND circuit A6
The gate signal E2 applied to one input of is at a low level, and no clock pulse is applied to the counter circuit A4. By setting the gate signal E2 applied to the AND circuit A5 at a high level at a desired timing, the counter circuit A
A clock pulse is applied to the input of 4 and the counting operation begins. The count value of counter circuit A4 is given to ROMA3 one after another in synchronization with the clock pulse, and
The address signal of A3 changes one after another, and ROM A3
The digital output values also change one after another.

As a result, the D/
The output voltage ES of the A converter A2 also changes over time, and the current flowing through the amplification control element (for example, a transistor) that constitutes the amplifier circuit A also changes over time. Therefore, the amplification degree to the amplifier circuit changes as It will change over time.

FIG. 3 is an explanatory diagram when a plurality of STC curve data are stored in the ROM. When a plurality of curves are stored as shown in the figure, the ROM address can be stored not only in the counter circuit A4 but also in the computer (CP), for example.
U) can be used to select. In the figure, the selection signal from the CPU is shown on the left, and the address signal from the counter circuit is shown on the right. In this way, C
A plurality of STC curves can be selected and used by the PU output.

〔Effect of the invention〕

As explained above, according to the present invention, the control voltage applied to the current control circuit or element can be determined based on the data in the memory device (ROM), so that the following many important effects can be obtained.

(b) Any STC curve can be created.

(b) By creating ROM data that matches the characteristics of the element that changes the amplification degree of the amplifier, it is possible to correct deviations in the STC curve due to deviations in characteristics and achieve the desired ideal ST.
A C curve can be created.

(c) If the purpose is different, any ST according to the surrounding situation
Since it is possible to create a C curve, the optimal STC can be determined depending on the surrounding situation.
Can be controlled.

(d) Storing multiple pieces of STC curve data in the ROM,
By selecting the address, a plurality of STC curves can be selectively used.

(e) It is most suitable as a computer-controlled STC amplifier 2.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a preferred embodiment of the present invention, FIG.
FIG. 3 is a waveform diagram showing the operation timing of the same embodiment, FIG. 3 is an explanatory diagram showing an example of data stored in the ROM, and FIG. 4 is a circuit diagram showing a conventional example. A...Amplifying circuit whose gain changes by controlling the current flowing through the constituent elements, A1...A circuit or element in which the current flowing through the constituent elements can be controlled by an externally applied voltage, A3...Storage device (RO(A4, A5)
. . . Data reading means, A2 . . . Means for converting digital data into analog voltage. V), Yio example 4 action hawk figure Figure 2 Figure 3 'jp Figure 14

Claims (1)

[Claims] An amplifier circuit whose gain changes by controlling the current flowing through the constituent elements, a circuit or element whose current flowing through the constituent elements can be controlled by an externally applied voltage, and a desired STC.
A storage device that stores curve data, a means for sequentially reading out the digital data stored in this storage device, and converting the read data into an analog voltage as a control input voltage for the current control circuit or element. an STC amplifier comprising means.