SU649123A1 - Dc small signal modulator - Google Patents

Description

The connected capacitor and load are connected to the common bus of the modulator.

Figure 1 shows the functional electrical circuit of the modulator; figure 2 - temporary diagrams illustrating his work.

The modulator contains a transistor 1, a source 2 of the signal to be converted, a source of 3 constant voltage, resistors 4-6, a peryjiHpyeNMft resistor 7, a diode 8, a capacitor of 9.10, a source 11 of the reference voltage, a load 12.

The pa6oTaet device is as follows.

In the absence of an input signal O and a broken circuit of the source 3 of direct current voltage, the emitter j of transistor 1 flows through the current j, which is equal to zero in the first approximation. Consequently, the output signal at load 12 will also be zero. The residual level of the emitter current of the highest order of smallness can be compensated by applying a constant bias twjwr to the collector junction. Compensation is achieved using a constant voltage source 3, a diode 8 and resistors 6 and 7. If there is a convertible signal Uj through the load 12 current flows and the output signal is

5xx-ctgflt expipUmSma) t), (i

t

where oLi --Ц- is the ratio of the base thickness of the transistor 1 to the diffusion length of the charge carrier;

 .TJ-r - load resistance 12, resistor L, respectively; one

| 5.- CT where K is a constant Boltzmann,

T is the temperature.

In order to avoid a dynamic surge of the output voltage in the modulator, it is sufficient to limit the frequency of the reference signal to some value f p, which is calculated as follows: there is no surge to load 12 under the condition

- h, (2)

.

-"- with

- capacitive coproop DL

emitter transition. Hence, with respect to the frequency of the reference signal, the condition is obtained:

one

(3)

Jjlt

For this modulator

1 10 ohm-5-10 and relative to the limiting frequency i we get:

, (3)

21 S 109 this one Asked by a 1% error, we get ip 310 PiT Thus, this modulator completely prevents the control reference signal from passing to the output when there is no input signal for ion ip. The voltage output at load 12 is due to the resorption effect of minority carriers in transistor 1 base is a necessary consequence of any impulse process

in pn-transitions. In this modulator, harmonic oscillations are used, the period of which is much longer than the resorption time of minority carriers, as a result of which the absorption effect does not affect the shape of the output signal. In addition, in this modulator, the zero level compensation is temperature stabilized, which also improves the accuracy of the conversion. The temperature dependence of the output voltage is determined by the residual level is

3 /)

-0

5) .. o. (

which can be compensated by applying the voltage Еg (csb) to the collector of the transistor 1, or setting a current in the collector circuit

, o (chc6-i).

Claims (1)

Invention Formula A small DC signal modulator containing a DC voltage source, a transistor whose emitter is connected via the first resistor with the output of the source of the signal to be converted, the base is connected to the output of the voltage source, and the collector is connected via the second resistor to the common bus of the modulator, a load characterized in that, in order to increase the conversion accuracy, a diode, an adjustable resistor, BC-circuit capacitor, and the collector of the transistor is connected through KS circuit with common modulator bus, through an adjustable resistor - with the cathode of the diode, the anode of which is connected to the negative pole of the constant voltage source, and the zmitter transistor through a series-connected capacitor and the load is connected to the common bus modulator. ,