SU1487160A1 - Amplitude discriminator - Google Patents

Description

The invention relates to a pulse technique and can be used in electronic measuring devices, in particular in measuring the recovery time of semiconductor diodes. View2

dropping an amplitude discriminator containing a differential cascade 1 on transistors 2, 3, source 4 threshold voltage, series-connected diodes 5, 6 of current mirrors 7, 8, series-connected variable resistors 9, 10 and tunnel diodes 11, 12, · capacitor 14, choke 15 and the source 16 of the reference voltage provides a stable and accurate separation of the collector current, which reduces the influence of the variation of the parameters of the tunnel diodes 11, 12 and provides an extension of the application of the discriminator. 3 il.

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1487160 A1

1487160

The invention relates to a pulse technique and can be used in electronic measuring devices, in particular in measuring the time of the reverse recovery of semiconductor diodes.

The purpose of the invention is to expand the scope by providing the possibility of eliminating the influence of the variation of parameters of tunnel diodes.

FIG. I presents a schematic diagram of the device; in fig. 2 - current-voltage characteristics of the tunnel diode; in fig. 3 - time diagrams explaining the work.

The amplitude discriminator contains a differential cascade 1 on transistors 2 and 3, the first input of which is connected to the threshold voltage source 4, and the collectors of transistors 2 and 3 are connected to a power source, respectively, through series-connected diodes 5, 6 and current mirrors 7 and 8, made on single-chip matched transistors, while the output shoulders of current mirrors 7 and 8 are connected to the zero potential bus, respectively, through series-connected variable resistors 9 and 10 and tunnel diodes 11, 12, with What are the outputs of the tunnel diodes 11 and 12 connected respectively to the terminals of variable resistors 9, 10? The second input of the differential stage 1 is connected to the input bus 13 via a capacitor 14 and connected via a choke 15 to a reference voltage source 16, resistors 17 and 18 and the capacitor 19 provide the mode of operation of the current source of the differential stage 1.

The device works as follows.

The constant current of the current source of the differential stage 1 is chosen slightly higher than 2 / max, where / max is the maximum current of the tunnel diodes 11 and 12 (Fig. 2, a and b).

In the initial state, transistor 2 is open, and transistor 3 is closed, because at the base of transistor 2, in the absence of input pulses, there is a higher potential than at the base of transistor 3 (ί / οπορ. >> // threshold. Where //opor.- voltage reference voltage, // threshold. - threshold voltage value).

All the current flows through the transistor 2 and is distributed equally between the branches a and b of the current mirror 6 and, therefore, a current much higher than the varnish will flow through the branch c through the tunnel diode 11 (Fig. 1). As a result, the operating point of the latter will be on the diffusion branch (point A in Fig. 2, a). Since the transistor 3 is closed, the operating point of the tunnel diode 12 is at the beginning of the tunnel portion of the current-voltage characteristic (point B in Fig. 2, b).

When a negative pulse arrives at the input of transistor 2, the current flowing through it decreases. Upon reaching the voltage pulse at the input of the transistor 2 threshold level Tsporog. at time Λ (Fig. 3a), the current of the source of the current of the differential stage 1 is distributed equally between the transistors 2 and 3, which causes the switching of the tunnel diode 12 from the tunnel section to the diffusion one. In this case, a positive voltage drop occurs on the tunnel diode (Fig. 3, b). Tunnel diode 11 with a decrease in current to / min, where / min - the minimum current of tunnel diodes (Fig. 2, a), switches from the diffusion branch to the tunnel and turns out to be prepared for repeated operation. When the pulse voltage at the base of the transistor 2 is equal again to the threshold voltage // threshold, at the time instant / ₂ (Fig. 3, a), the tunnel diode 11 passes from the tunnel portion to the diffusion one. In this case, a positive voltage drop occurs in the tunnel diode (Fig. 3, d), and the device returns to its original state.

In the absence of input pulses, the entire current of the source of the current of the differential stage 1 flows through transistor 2, and since it is 2 / max., The tunnel diode directly connected to the collector circuit operates in a busy state most of the time. The shunting of a tunnel diode with a current-voltage characteristic coinciding with the diffusion branch of the current-voltage characteristic of a tunnel diode eliminates the heavy duty of the circuit, but requires careful selection of the shunt diode to achieve accuracy discrimination. The inclusion of a tunnel diode in the composition of the current mirrors (Fig. 1) eliminates the stress mode (increases reliability) and provides high accuracy of discrimination in a wide temperature range.

The time interval between the positive pulses (Fig. 3, a and b) will be more stable than the duration of the pulses on the tunnel diodes (Fig. 3, b and d). This is explained by the fact that the process of reverse switching of tunnel diodes differs in time from direct switching (it is characterized by a large response delay and a large instability of this delay).

Using positive pulses at the outputs 1 and 2 (Fig. 1), it is possible to fix the moments of time when the voltage of the input pulse is equal to the threshold.

Variable resistors 9, 10 included

in series with tunnel diodes 11,

12, deform the corresponding current

mirrors, thereby excluding the selection of tunnel diodes. Current mirrors built

1487160

on single-chip matched transistors, which ensures the accuracy of the amplitude discriminator in a relatively wide temperature range.

Claims (1)

Claims $ Amplitude discriminator comprising differential stage transistors, a first input of which is connected to a source of threshold voltage, and in kol lecturer first transistor ¹⁰ is turned on the first diode, the input signal source, tunnel diodes, characterized in that, in order to expand applications by providing the possibility of eliminating the influence of variation in the parameters of tunnel diodes, A capacitor, a choke, a second diode, a reference voltage source and two current mirrors, made on single-crystal matched transistors, whose input arms are connected via diodes in the forward direction to the collectors of the differential cascade, are connected to the zero potential bus through serially connected variable resistors and tunnel diodes, the tunnel diode output connected to the variable resistor output being the device output, the second input is di The differential cascade is connected to the input bus through a capacitor and through a choke to the reference voltage source. Fiz2 1487160