CS240667B1 - Switching on the triggering circuit for measuring signals - Google Patents

Abstract

The invention falls within the field of measurement technology and solves the trigger circuit from integrated circuits achieving a large input resistance to the measured signal, a defined voltage transfer with small hysteresis with ensured temperature stability. The problem was solved by connecting a compensating emitter follower of the PET type to the non-inverting input of the integrated logic comparator, connected via an adjustment potentiometer to a source of positive and negative compensation levels, i.e. an emitter follower of the same type as in the signal branch, connected to the inverting input of the comparator, to whose output a logic circuit equipped with a switch for setting the trigger polarity is connected. The connection of the compensating emitter follower (T2) and the logic circuit (2) best characterizes the invention

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a trigger circuit for measuring signals with a FET-type input transistor connected to an emitter tracker connected to an inverting input of an integrated logic comparator.

Circuitry of discrete elements or integrated circuits to achieve high speed and sensitivity are known, but high input resistance, thermal stability and defined low-voltage voltage transfer are very difficult to achieve.

The aforementioned disadvantages eliminate the circuit according to the invention, which is based on the fact that a non-inverting input of the integrated logic comparator is connected via a symmetrical resistor to a FET-type transistor in the connection of an emitter follower. A comparative level source is connected to its input via a setting potentiometer and a second filter element by means of a first switch, and a logic circuit provided with a second switch for adjusting the trigger polarity is connected to the output of the integrated logic comparator.

The circuitry of the present invention compensates the voltage transmission and temperature drift of the FET input emitter tracker to achieve high input resistance, the circuitry being formed on integrated circuits to achieve high speed, sensitivity, and stability.

240 607

An example of a trigger circuit according to the invention is further described with reference to the drawing wherein 1 denotes an integrated logic comparator whose inverting input connects the output of a PET input transistor T1 in an emitter follower whose current is set by a third resistor R3 and the measured AC or DC signal is introduced via the high input impedance R1 via a limiting resistor R2, bridged by compensation capacitor C2 compensating for its AC transmission attenuation. Between the base of the input transistor T1 and its power supply, polarized diodes D1 and D2 are connected in an impermeable direction forming an overvoltage protection circuit with a limiting resistor R2. The first filter element R6, C6 is connected to the emitter output of the input transistor T1.

The non-inverting input of the integrated logic comparator 1 is connected via the balanced resistor R7 to the output of the compensating transistor T2 also of the PET type in the connection of the emitter follower whose current is set by the fourth resistor R4. with the first switch U source + U, —U of the comparative voltage. The eighth resistor R8 creates the flip hysteresis of the integrated logic comparator 1. Due to the one-polar level of the output of the integrated logic comparator 1, its output is provided with a logic circuit 2 with polarity switching +/- by a second switch Př2.

The level of the comparison level and the first switch at its polarity are set with the setting potentiometer PI. Simultaneously, the second switch Př2 of the logic circuit 2 sets the trigger polarity. Changing the logic level at its output signals reaching the preset level of the polarity.

Another possibility of use is in those circuits where it is a precise triggering or synchronization, derived from the adjustable value of the analog signal. Advantages include high input resistance, sensitivity, stability and compatibility with the following digital logic. In measuring technology it is possible to use it in oscilloscopes or in transieut recorder in which the circuit is used.

Claims (1)

P S £ D OF THE INVENTION 240 667 A trigger circuit for measuring signals with a PET input transistor in an emitter follower connected to the inverting input of the integrated logic comparator, characterized in that a compensating transistor (T2) is connected to the non-inverting input of the integrated logic comparator (1) FET in emitter follower, to which input is connected (+ U, -U) comparative level source (+ U, -U) via the setting potentiometer (Pl) and second filter element (R5, C4) to the output of integrated logic comparator ( 1) a logic circuit (2) equipped with a second switch (Př2) for setting the trigger polarity is connected.