HU208202B - High-hysteresis comparator for basic oscillators of the function generators - Google Patents

Abstract

- (Dwg.1/1)

Description

Scope of the description: 10 pages (including 3 sheets)

HU 208 202 B is connected to one end of the fifth and sixth resistors (R5, R6) and to the base of the seventh transistor (TR7). The collector of the second transistor (TR2) at one end of the seventh and eighth resistors (R7, R8) and the base of the eighth transistor (TR8) at one end of the first and second resistors (R1, R2) of the base of the third transistor (TR3) and a fifth transistor ( TR5), the emitter is connected to the emitter of the fourth transistor (TR4) and to a pole of the first current generator (II). The base of the fourth transistor (TR4) is connected to one end of the third and fourth resistor (R3, R4) and to the collector of the sixth transistor (TR6), to one end of the collector ninth resistor (R9) and to the collector of the eighth transistor (TR8), which is also a high-hysteresis comparator. output (OFF). The other end of the second resistor (R2), the other pole of the first current generator (II) and the other end of the fourth resistor (R4) is the negative voltage (-U _T ), the other pole of the negative voltage generator (U _L ) is the fifth transistor (TR5) , the emitter of the fifth transistor (TR5) is connected to the emitter of the sixth transistor (TR6) and to the collector of the seventh transistor (TR7). The emitter of the seventh transistor (TR7) is the emitter of the eighth transistor (TR8) and one of the poles of the second current generator (12), the other end of the sixth resistor (R6), the other pole of the second current generator (12) and the other end of the eighth resistor (12). the other end of the positive voltage (U _T ), the first, the third, the fifth, the seventh and the ninth resistors (R 1, R 3, R 5, R 7, R 9) and the base of the second and sixth transistors (TR 2, TR 6) and it connects to the ground.

The present invention relates to a high hysteresis comparator for a base oscillator of function generators, which controls the charge-discharge system of the base oscillator by comparing the voltage level of the timer capacitor to two reference voltage levels.

Its field of application is in function generators for industrial and laboratory use, as well as other charging sources.

There are several solutions for implementing a high hysteresis comparator. It represents the technical level eg. is also a widely used solution in the WAVETEK 171 function generator as shown in Figure 1. The operation of the circuit arrangement is described in conjunction with the base oscillator components for ease of understanding.

If the output level of the high hysteresis comparator (IC) is positive, this voltage level controls (IA) the current gate controlled by (1D) by enabling the positive (+ I _T ) timer current to be enabled. This current charges the timing capacitor (C _T ), where the voltage rises linearly. This voltage is delivered to the high-hysteresis comparator (BE) input (IC) via the unit gain (IB) isolation amplifier. When reaching the voltage level generator (U _H ) voltage generator (U _H ) that determines one switching level, the high hysteresis comparator (IC) switches over and switches off the positive (+ I _T ) timer current on the rectangular signal isolator amplifier (1D) and the current-controlled (I). and it also turns on the negative (-I _T ) timer current. The discharging or negative charging of the timer capacitor (C _T ) begins. The discharge lasts until the voltage level of the level-shift negative (U _L ) voltage generator that determines the second switching level. At this point, the high hysteresis comparator (IC) recalculates the positive (+ I _T ) timer current again and thus starts charging in a positive direction. A period of the triangle signal was created.

The structure of (IC) high hysteresis comparator is a zero voltage comparator. Switching is always done when the (OV) voltage level crosses, the switching levels are set with level switches implemented with positive and negative (U _H and U _L ) voltage generators.

The known solution includes a differential amplifier consisting of three first and second, third and fourth, fifth and sixth (TR11, TR12, TRI3, TRI4, TRI5, TR16) transistors, and a controlled current generator consisting of two seventh and eighth (TRI7, TRI8) transistors. Differential amplifiers consisting of the third and fourth transistors TR13, TRI4 and transistors 5 and 6 (TR15, TR16) operate as a zero voltage comparator. In the case of positive charge, the comparator output is positive because the second (TRI2) transistor leads, the current generates a positive output voltage through the sixth and seventh (R16, R17) resistors. At the common point of the voltage distributor consisting of the sixth and seventh (R16, R17) resistors, a voltage is generated by switching off the current generator with the eighth (TRI8) transistor. The fifth, sixth (TR15, TR16) differential amplifier, which monitors the negative (U _L ) voltage generator switching level, receives no current.

The control of the second transistor TR12 is provided by a fourth transistor (TR14) of a third amplifier (TR14) supplied by a current generator implemented by a seventh (TRI7) transistor. The current generator of the seventh (TR17) transistor is in the enabled state because the current (TR11) of the first transistor (TR11) is deactivated by the second (TRI2) transistor. The system is at rest.

Figure 1 shows that the voltage of the positive-voltage positive generator (U _H ) is subtracted from the instantaneous voltage of the triangle signal. Since the base of the fourth transistor (TRI4) is connected to a voltage (OV), the switching occurs exactly when the voltage of the positive (U _H ) voltage generator is reached. Then the third transistor (TR13) starts to drive and draws the current of the fourth transistor (TRI4).

A differential amplifier consisting of a first transistor (TR11, TR12) controlled by them is also tilted.

HU 208 202 B

The first transceiver (TR11) that enters the conduit disables the current generator of the seventh (TR17) transistor, and the second transistor (TR12) to be closed terminates the blocking of the current generator implemented by the eighth (TR18) transistor. The first (TR11) transistor is held in control and the fifth transistor (TR15) enters the drive at the switching moment. The collector of the second transistor (TR12), which at the same time forms the output of the circuit arrangement (OFF), is negative. This level disables the positive (+ I _T ) timing current through the rectangular signal selector amplifier (1D) and the current gate current (1A), while also allowing the negative (-I _T ) timer current to start discharging or charging the negative (C _T ) timer capacitor. direction. When the voltage of the timer capacitor (C _T ) reaches the voltage of the negative (U _L ) voltage generator, by switching off the fifth transistor (TR 15), the differential amplifier consisting of the fifth, sixth (TR 15, TR 16) transistor switches, so the first, second (TR 11, TR12) a transceiver differential amplifier also switches. The second transistor (TR12) entering the conductor disables the current generator of the eighth (TR18) transistor, and the first transistor (TR11) in the closure allows the operation of the current generator with the seventh (TR17) transistor. The differential amplifier consisting of the first transistor (TR11, TR12) is maintained by a third amplifier with a fourth transistor (TR13, TR14). The output of the comparator (OFF) jumps to a positive level, charging starts in the positive direction as already described.

A period of the triangle signal was created.

The shortcomings of the known technical solution are the following

- the high hysteresis comparator detects the positive switching level by introducing the comparator transistor into the lead, while the negative switching level is detected by switching off the comparator transistor. This is due to the structure of the circuit, because differential amplifiers of NPN type transistors are used for both tasks, and thus switching is asymmetric,

- the comparator output rectangle is active only on the positive rising edge. The characteristics of the negative edge of the rectangular signal are determined only by the sixth, seventh (R16, R17) passive members. Since the sixth, seventh (R16 and R17) resistors cannot be arbitrarily accompanied, the output impedance cannot be reduced below a given value, and consequently, and as a result of the scattered capacities, the negative downward edge of the rectangular signal will be slower than the positive rising edge.

The object of the invention is to overcome the drawbacks of the known solution and to create a high hysteresis comparator in which the output rectangular signal is active not only on the positive rising edge, but also on the negative downward edge and the switchover is completely symmetric in two stable states.

The present invention is based on the discovery that the achievement of a positive switching level is detected by NPN type, and that a negative switching level is achieved by differential amplifiers built from PNP type transistors, such as zero comparators, and by each of the zero comparators on a differential amplifier controlled by the same comparator level sensor. through a current generator generating an emitter current, a high hysteresis comparator with a completely symmetric structure with two stable states is created whose active output level becomes a sign at the moment of reaching the comparing levels, also considering the direction of the change of the input signal.

The present invention therefore relates to a high hysteresis comparator for the base oscillator of a generator of generators, which has a positive and negative voltage generator, a positive and a negative supply voltage, and a ground point for determining a level switch. The coupled pole of the positive and negative voltage generators is also the input of the high hysteresis comparator to which the output of the base oscillator isolator amplifier is connected, the output of the high hysteresis comparator is connected to the input of the controlled current gate of the base oscillator.

The high hysteresis comparator is characterized by the fact that the other pole of the positive voltage generator is connected to the base of the first transistor, the emitter of the first transistor to the emitter of the second transistor and the collector of the third transistor, the collector to one end of the fifth and sixth resistors, and to the base of the seventh transistor. The collector of the second transistor is connected to one end of the seventh and eighth resistors and to the base of the eighth transistor, one end of the first and second resistors of the base of the third transistor, and the fifth transistor collector, the emitter is connected to the emitter of the fourth transistor and one pole of the first current generator. The base of the fourth transistor is connected to one end of the third and fourth resistor, and to the collector of the sixth transistor, the collector is connected to one end of the ninth resistor and the collector of the eighth transistor, which also forms the output of the high hysteresis comparator. The other end of the second resistor, the other pole of the first current generator, and the other end of the fourth resistor, the second pole of the negative voltage generator is connected to the base of the fifth transistor, the emitter of the fifth transistor is connected to the emitter of the sixth transistor and the collector of the seventh transistor. The emitter of the seventh transistor is the emitter of the eighth transistor and one of the poles of the second current generator, the other end of the sixth resistor, the other pole of the second current generator, and the other end of the eighth resistor, the second is the third, fifth, seventh and ninth resistor and the base of the second and sixth transistors is connected to the ground.

The drawings which are known and described in accordance with the present invention are as follows:

Figure 1 shows the known high hysteresis comparator;

Figure 20 shows the high hysteresis comparator of the present invention and the base oscillator components, and Figures 3a to 3f show the time diagrams of the high hysteresis comparator according to the invention.

Figure 2 shows the components of the high hysteresis comparator and base oscillator of the present invention, the high hysteresis comparator is framed by a dashed line in the drawing and labeled 1C as a subset of the base oscillator. The high hysteresis comparators have a switching level, a positive and negative (U _H , U _L ) voltage generator, a positive and negative (U _T , -U _T ) voltage generator with a ground point. The connected pole of the positive and negative (U _H , U _L ) voltage generator is also the input of the high hysteresis comparator (BE) to which the output of the isolator amplifier (1B) of the base oscillator is connected, the output of the high hysteresis comparator (OFF) is the base oscillator (1A). is connected to the input of a controlled current gate. The high hysteresis comparator is characterized by the fact that the other pole of the positive (U _H ) voltage generator is on the base of the first (TR1) transistor, the emitter of the first (TR1) transistor emitter and the collector of the third (TR3) transistor, the collector is fifth and sixth (R5). , R6) is connected to one end of the resistor and to the base of the seventh (TR7) transistor. The second (TR2) transistor collector at one end of the seventh and eighth (R7, R8) resistors, and at the base of the eighth (TR8) transistor, the third (TR3) transistor base at one end of the first and second (R1, R2) resistors and the fifth (TR5). ) to the transistor collector, the emitter is connected to the emitter of the fourth transistor (TR4) and to one pole of the first (II) current generator. The base of the fourth (TR4) transistor is connected to one end of the third and fourth (R3, R4) resistors and to the collector of the sixth (TR6) transistor, to one end of the collector resistor (R9), and to the collector of the eighth (R8) transistor, which is also a large hysteresis comparator (OFF) output. The other end of the second resistor (R2), the other pole of the first (II) current generator and the other end of the fourth resistor (R4) for the negative (-U _T ) power supply, the other pole of the negative (U _L ) voltage generator is the fifth transistor (TR5). , the emitter of the fifth transistor (TR5) is connected to the emitter of the sixth (TR6) transistor and to the collector of the seventh (TR7) transistor. The emitter of the seventh (TR7) transistor is the emitter of the eighth (TR8) transistor and the second (12) of the current generator, the other end of the sixth (R6) resistor, the other pole of the second current generator (12), and the other end of the eighth (R8) resistor. positive (U _T ) power supply, the other end of the first, third, fifth, seventh and ninth (R 1, R 3, R 5, R 7, R 9) resistors, and the base of the second and sixth (TR 2, TR 6) transistors connected to the ground.

The operation of the high hysteresis comparator according to the invention according to Figures 2 and 3 is as follows:

At the time of power-up, the time capacitor (C _T ) is in the discharged state with the voltage (OV) on it (U _CT ). This voltage is applied to the input of the high hysteresis comparator (BE) via the isolating amplifier (1B) and then has the following state:

Ul <U _CT <U _H.

The correct operation of the high hysteresis comparator requires that the current of the first (II) current generator is the first comparator consisting of the first transistor (TR1, TR2), and the current of the second current generator 12 from the fifth, sixth (TR5, TR6) transistors. to a standing comparator. This is true when U3 <U4 and Ul> U2, where U3 is the voltage on the fifth (R5) resistor, U4 is the voltage on the seventh (R7) resistor, Ul is the voltage on the first resistor (R1), U2 is the third voltage (R3) resistor voltage. Then the current of the first (II) current generator to the differential amplifier consisting of the first, second (TR1, TR2) transistor, and the current of the second current generator (12) via the seventh (TR7) transistor, via the opening (TR3) transistor, is the fifth, sixth. (TR5, TR6) to a differential amplifier consisting of a transistor. This requires that

R1 R3

R1 + R2 ^< R3 + R4 &lt; ^tb &gt;

The first stable state after switching on, with the difference in the recovery time of the positive and negative (U _T , -U _T ) supply voltage, on the third, second and eighth (TR3, TR2, TR8) transistors, and on the seventh, sixth and fourth ( TR7, TR6, TR4) determine the delay time of the current paths passing through transistors.

Suppose that the current path through the third, second and eighth (TR3, TR2, TR8) transistors is faster. In this case, the current stream of the first (II) current generator travels through the open transistors 3 and 2 (TR3, TR2) to open the eighth (TR8) transistor, which draws the current of the second (12) current generator from the slower, seventh and sixth. (TR7, TR6) from a current path through transistors. At one end of the ninth (R9) resistor (at its hot point), which is also the output of the high hysteresis comparator (KI), a positive output signal is generated as shown in Figure 3b. The high hysteresis comparator is in a stable state because the seventh, sixth and fifth transistors (TR7, TR6, TR5) do not receive power, and the eighth (TR8) transistor conductor state is the voltage (Ul) on the first (R1) resistor. the third (TR3) transistor leading to the supply of voltage (U2) on the third resistor (R3) is provided by the current through the second transistor (TR2). The high-level hysteresis comparator positive-level output allows the positive (+ I _T ) timer current through the current-controlled current port (1A), and the timer capacitor charger (C _T ) starts.

Positive direction. The (C _T ) timer capacitor (U _CT ) voltage is applied to the high hysteresis comparator (BE) via the isolator (1B). Positive charge continues until the voltage (C _T ) of the capacitor (U _CT ) reaches the voltage level of the positive voltage generator (U _H ). When (U _CT = U _H ), at this point in time, the first transistor (TR1) starts to drive and draws off the current of the second transistor (TR2), so that the first amplifier consisting of the second transistor TR1 (TR2) traverses. The first (TR1) transistor on the collector collector has a negative polarity, and the second (TR2) transistor collector has a positive polarity voltage jump, which leads to the seventh (TR7) transistor conductor, and the eighth (TR8) transistor is closed. The current of the seventh (TR7) transistor to be led leads through the sixth (TR6) transistor to open the fourth (TR4) transistor, which is the first, second, third (TR1, TR2, TR3, TR1, TR2) monitoring the positive switching level by withdrawing the current of the first (II) current generator. ) switches off transistor.

The fourth transistor (TR4) to be introduced into the conductor on the ninth (R9) resistor generates a negative output level proportional to the current of the first (II) current generator. This voltage value disables the positive (+ I _T ) timing current through the current-controlled current port (1A), and allows the negative (-I _T ) timer current to start charging in the negative direction (C _T ). The seventh differential amplifier consisting of the eighth (TR7, TR8) transistor thus ensures the stable state of the high hysteresis comparator after switching over by observing the voltage difference U3 <U4. The negative charge of the timing capacitor (Cp) continues until the linearly negative (U _CT ) voltage on it does not reach the voltage value of the leveling negative (U _L ) voltage generator. If (U _CT - U _t ), at this point in time, the fifth (TR5) transistor starts to drive and draws the current of the sixth (TR6) transistor, and thus the fifth differential transducer (TR5, TR6) consisting of sixth transistor will cross . The fifth (TR5) transistor collector collector has a positive polarity, and the sixth (TR6) transistor collector has a negative polarity voltage jump, which causes the third (TR3) transistor conductor and the fourth (TR4) transistor to be closed, the third in the lead ( TR3) transistor current through the second (TR2) transistor controls the eighth (TR8) transistor, which bypassing the current of the second current generator (12) disables the fifth, sixth, seventh (TR5, TR6, TR7) transistor monitoring the negative switching level.

The eighth (TR8) transistor to be guided generates a positive output level proportional to the current of the second (12) current generator at the ninth (R9) resistor. This level disables the negative (-I _T ) timer current through the current-controlled current port (1A), and allows the positive (+ I _T ) timer current to start charging the (Cp) timer capacitor in a positive direction. The third differential amplifier consisting of the fourth transistor TR3 (TR4) thus ensures the stable state of the high hysteresis comparator after switching over by observing the voltage difference (Ul) <(U2).

At the end of the positive charge half-life, a period of the baseline oscillator output signal has been completed and a new period begins when the level-shift positive (U _H ) voltage generator is reached.

The objectives of the high hysteresis comparator according to the invention have been realized and the following are the advantages:

- the output for the rectangular signal is active not only on the positive rising edge, but also on the negative downward edge,

- the switchover is completely symmetrical, in two stable states defined by the positive and negative level generator of the leveling device,

- the rectangular separator amplifier required for the known solution may be omitted.

Claims (1)

Patent Claim Point High-hysteresis comparator for the base oscillator of function generators with positive and negative voltage generators (U _T , -U _T ) defining a level shift positive and negative voltage generator (U _H , U _L ) defining a switching level, positive and negative voltage generators (U _H , U _L ) is connected to one of the poles of the high hysteresis comparator input (ON) to which the output of the isolator amplifier (1B) of the basic oscillator is connected, the output of the high hysteresis comparator (OFF) is connected to the another pole of a voltage generator (U _H ) to the base of the first transistor (TR1), the emitter of the first transistor (TR1) to the emitter of the second transistor (TR2) and to the collector of the third transistor, one of its fifth and sixth resistors (R5, R6); ) base price, the second transistor a collector of r (TR2) at one end of the seventh and eighth resistors (R7, R8) and at the base of the eighth transistor (TR8), at one end of the first and second resistors (R1, R2) of the third transistor (TR3) and the fifth transistor (TR5). to the collector, to the emitter of the fourth transistor (TR4) and to a pole of the first current generator (II), to the base of the fourth transistor (TR4) at one end of the third and fourth resistors (R3, R4) and to the collector of the sixth transistor ) and to the collector of the eighth transistor (TR8), which also forms the output (KI) of the high hysteresis comparator, the other end of the second resistor (R2), the other pole of the first current generator (II) and the other end to the negative supply voltage (-U _T ), the other pole of the negative voltage generator (U _L ) to the base of the fifth transistor (TR5), the fifth transistor The emitter of the (TR5) to the emitter of the sixth transistor (TR6) and the collector of the seventh transistor (TR7), the emitter of the seventh transistor (TR7) to the emitter of the eighth transistor (TR8) and one of the poles The other end of position B (R6), the other pole of the second current generator (12) and the other end of the eighth resistor (R8) to the positive supply voltage (U _T ), the first, third, fifth, seventh, and ninth resistance (RI, R3, R5, The other end of R7, R9) and the base of the second and sixth transistors (TR2, TR6) are connected to ground.