SU368719A1 - FIXATION DEVICE - Google Patents

Description

one

The invention relates to measuring radar technology.

A device for fixing a predetermined initial signal level is known, made on the basis of a differential amplifier on np - “- transistors with a dc generator in a common emitter circuit containing in the negative feedback circuit a collector. And a second transistor of a differential amplifier connected to the base to the source of the reference voltage, to the base of the first transistor of the differential amplifier, connected to the input source through a coupling capacitor, a storage capacitor, and two p-p- p-transistor a.

The purpose of the invention is to increase the stability of fixing the initial level of the input signal to a 1H1H nom in a wide dynamic range of the input signal.

It is achieved by the fact that the storage capacitor is connected to the base of the input transistor of the differential amplifier through the base-collector junction of a pn-transistor connected to the common emitter circuit, and to the collector of the second transistor of the differential amplifier through the base-emitter junction of pnp-p- a transistor connected in a circuit with a common collector, the base of the input transistor of the differential amplifier being connected to the negative pole of the power source by means of a direct current generator on a pn-pt anzistore.

The drawing is a diagram of the proposed device.

The device contains a capacitor 1, a current generator of capacitor 1 discharge on the transistor 2, a differential amplifier on

transistors 3, 4 with a current generator on transistor 5, a feedback circuit consisting of transistors 6, 7 and a capacitor 5, a resistor 9, and an incomplete diode thermal compensation circuit 10.

The specified latching potential of the initial low level of the input signal goes to the base of transistor 4. In the absence of an input signal, the circuit is set up so that the currents of the transistors are equal and sum up the current of the transistor 5. The current generator on the transistor 5 is necessary the fixation level is the equality of the currents of the transistors 4 and 3 and their total value is preserved.

The collector current of transistor 4 creates a voltage drop across resistor 9. The magnitude of the resistor is chosen such that transistor 7 is open and its collector current is equal to the generator current at transistor 2.

Since the currents of transistors 3 and 4 are equal, the potentials of the bases of these transistors are also equal. 3iTO steady state circuit.

Suppose the potential of the base of transistor 3 decreases slightly. Due to the fact that the base potential of transistor 4 is set externally and independent, transistor 3 decreases, the current of transistor 4 increases, since the sum of the currents of the transistors is unchanged and is determined by the current of the transistor 5. An increase in the current of transistor 4 causes an increase in the voltage drop across the resistor 9. Through the transistor 6, the capacitor 8 is charged, and the voltage drop across it increases. This leads to an increase in the current of the transistor 7. The increment of the collector current of the transistor 7 additionally charges the capacitor /, which leads to an increase in the potential of its right side plate, i.e., to the restoration of the potential of the base of the transistor 3.

Thus, the potential of the base of the transistor 3 is automatically fixed, equal to the base potential of the transistor 4. The initial spread of the characteristics of the transistors 3 w 4, as well as the magnitude of the voltage drop in the circuit 10, constitute a certain shift of the fixed potential relative to the given one. But this shift is systematic and does not depend on the level of fixation, temperature, and. etc. It should simply be taken into account when setting the fixation level.

When a signal appears at the base of transistor 3, the same potential corresponds to the minimum signal level, since if the signal component drops below the fixed level, this will cause a decrease in the current of transistor 3, an increase in the current of transistor 4, a charge capacitor S and a sharp increase in the current of the transistor 7, which will lead to an increase in the potential of the base of the transistor 3. The positive components of the signal close the transistors 4 and 5 and do not affect the discharge of the capacitor 8, therefore the current of the transistor 7 remains the same as the current of the transistor 2 of the torus due to something or discharge capacitor / occurs. Naturally, the time constant, equal to the product of the value of the capacitor 8 by the input resistance of the transistor 7, must be greater than the duration of the positive input signal.

In order to provide a magnitude of the current gain factor {| 3) of the transistor 7, which is close to the nominal value, a current of 1-3 mA should be set through this transistor. With such a collector current of the transistor 7, the influence of the uncontrolled current / k „of this transistor on

the operation of the circuit is excluded, since its constituent in the Common collector current is negligible. The element that sets the collector current of transistor 7 uses a current generator on transistor 2. The use of a current generator as a driving element is due to the need to increase the input resistance of the fixation circuit and to ensure independence of the fixation level from the amplitude of the input signal and the magnitude of the fixing potential.

The use of a differential amplifier as an element of comparison of a given level of fixation with a minimum value

The non-temporal component of the input signal creates the prerequisites for good thermal stability of the circuit. A slight temperature instability (9 mV) created by the feedback circuit is selected by the circuit 10 of the incomplete diode thermal compensation. The magnitude of the thermal compensation voltage is determined by the resistor of the circuit 10.

Subject invention

A device for fixing a given initial signal level, made on the basis of a differential amplifier on pn-transistors with a DC generator in a common emitter circuit, containing in the negative feedback circuit a collector. And the second transistor of a differential amplifier connected to the source

a reference voltage, to the base of the first transistor of a differential amplifier connected to an input source through a coupling capacitor, a storage capacitor, and two pnp transistors, characterized in that, in order to increase the stability of fixing the initial level of the input signal at a given level In a wide dynamic range of the input signal, the storage capacitor is connected to the base of the input transistor. Differential amplifier through the base-collector junction of the p-to p-transistor, included circuit with a common emitter, and to the collector of the second transistor of the differential amplifier through the base-emitter non-junction of a pnp transistor connected in a circuit with a common collector, the base of the input transistor of the differential amplifier connected to the negative pole of the power source by a constant-power generator current on pp - “- transistor.

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