DE2346931A1 - TRANSISTOR CIRCUIT WITH HYSTERESIS PROPERTIES - Google Patents

Description

Dipl.-Ing. H. MiTSCHERLICH 8 MONKS

Dipl-lng. K. GUNSCHMANN SfeinidorfetraiJe 10

Dr. rer. not. W. KÖRBER. »Pen) ·» ««!

Dipl.-Ing. J. SCHMIDT-EVERS 2346931

PATENT LAWYERS

18th September 1973

SONY CORPORATION
7-35 Kit as hinagawa
6-chome, Shinagawa-ku
Tokyo / Japan

Patent application

Transistor circuit with hysteresis properties

The present invention relates generally to a transistor circuit having hysteresis properties, in particular, it is directed to an improved transistor circuit having an output signal results in a first level until an input signal reaches a first threshold voltage, whereupon the output signal maintained at a second level until the input signal voltage falls below a second threshold drops, which is different from the first threshold voltage, for example lower.

Among the known transistor circuits with hysteresis

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properties become the most due to their simplicity the Schmitt trigger circuits are generally or extensively used. The Schmitt trigger circuits, however, just like other known transistor circuits with hysteresis properties are disadvantageous in that such circuits input signals with a relatively high level for reliable operation of these Require circuits. In the existing Schmitt trigger circuits, there is also the change in the output signal voltage can be brought about, i.e. the range of change in the output signal voltage in Relatively small depending on the input signal in relation to the supply voltage for operation the circuit. A disadvantage of the existing Schmitt trigger circuits is also that the range of change or setting the output signal voltage is not independent of the difference between the input signal threshold voltages can be provided, which the circuit from a first state to a second Trigger or control state or from the second state back to the first state. These disadvantages of existing Schmitt trigger circuits lead to serious design problems in certain fields of application the same, such as when using a Schmitt trigger circuit in the color killer circuit of a Color television receiver.

Accordingly, an object of the present invention is to provide a transistor circuit having a hysteresis property, in which the above-described disadvantages and problems of the prior art are avoided.

In particular, the object of the present invention is to provide a transistor circuit with a hysteresis'

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property that consists of a minimal number of components in a simple circuit design exists and is particularly suitable to be formed as an integrated circuit «Another goal is to create a transistor circuit with a hysteresis property caused by an input signal can be operated at a relatively low level

Another object is to provide a transistor circuit of the type described above in which the Difference between the threshold voltages for driving of the circuit between its two states regardless of the range of change in the output signal voltage can be designed, with this range of change in the output signal voltage in particular be relatively large in relation to the supply voltage for operating the circuit can"

According to one feature of the invention, there is a circuit with a hysteresis property which a first and a second transistor, each of which has a control or base electrode and a first and second electrodes, such as a collector and emitter electrode, between which a current conducting path or path is formed when a control voltage which exceeds a predetermined value, is applied to the corresponding control electrode, with an input signal through a resistor is applied to the control or base electrode of the first transistor, and this control or Base electrode preferably through a second transit gate «It is the first or collector electrode of the second

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Transistor is connected and one side of a feed tower source, such as your side, which gives a relatively high positive potential, preferably connected through a load resistor to the first or collector electrode of the first transistor is, while this first or collector electrode is also connected to a signal output terminal and preferably is connected to the control or base electrode of the second transistor through another resistor, wherein the second or emitter electrodes of the first and of the second transistor directly to the other side of the supply current source, for example at Erdoder Reference voltage are connected.

So, it becomes a transistor circuit having a hysteresis property created, which is provided with a first and a second transistor, each of which is a control or Base electrode and a first and second additional electrode, for example collector and emitter electrodes has, between which a current-conducting path is formed when the transistor is switched on by a control voltage which to the corresponding control electrode is applied exceeding a predetermined value, wherein an input signal is applied to the control electrode of the first transistor through a resistor, and this control electrode is preferably connected to the first electrode of the second transistor through a resistor is, and one side of a power supply source through a load resistor with the first electrode of the first transistor is connected and this first electrode is also connected to an output terminal and preferably through another resistor is connected to the control electrode of the second transistor, while the second

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Electrodes of the first and the second transistor are immediate or low-resistance connections to the other side of the power supply source, for example with Have earth »

In the above circuit arrangement according to the invention, the absence of any reactive elements makes the Circuit particularly suitable as an integrated circuit formed on a single semiconductor die to become. The direct or low-resistance connections of the second or emitter electrodes of both Transistors to ground also allow the circuit to be controlled by an input signal of a relatively is operated reliably at low levels. The circuit arrangement described is also particularly advantageous, because the difference between the input signal threshold voltage levels, which give the hysteresis property regardless of the range of change of the output signal voltage, and also because the range of change in the output signal voltage almost as great as the voltage of the supply current source can be made.

The above and other objects, features, and advantages of the present invention will be apparent from the following detailed description of an 'embodiment of the invention in conjunction with the accompanying drawings; show in it:

1 shows a circuit diagram of a Schmitt trigger circuit with hysteresis properties according to the prior art;

Fig. 2 is a circuit diagram of a transistor circuit with a Hysteresis property according to one embodiment of the present invention;

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Figure 3 is a graphical representation of an input signal increasing linearly with time and then linearly decreases and the state of a transistor in the circuit according to the invention in different Displays times during this input signal;

Fig. ^ Is a graph showing the relationship of the input signal according to Fig. ' 3 to the output signal from the circuit according to the present invention, its hysteresis property is also shown; and

Fig. 5 is a block diagram of a color television receiver; in which the transistor circuit according to FIG. 2 is used as a color killer circuit.

Before describing the transistor circuit having a hysteresis property of the present invention and in order to better understand the problems overcome by the present invention, reference is first made to Fig. 1 which shows a typical Schmitt trigger circuit of the type used in the prior art is widely used when a hysteresis property is required. In the illustrated Schmitt trigger circuit, an input or switching signal E., which is received by an input _{terminal 1, is applied to the base electrode of an input transistor Q 1} , the collector electrode of which is connected through a collector transistor 1 to a terminal 3, which has a supply voltage ⁺ V receives from a side (not shown) of a power supply source. The other side of the supply current source, which is at ground or reference potential

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can be connected by a common emitter resistor _R2 to the emitter electrode of the transistor Q _1, and also to the emitter electrode of an output transistor Q ₂ · The collector electrode of transistor Q ₁ is formed by a parallel circuit of a speed-up capacitor C> and a level shift and Kupp lungs resistor R _{3 is} connected to the base electrode of transistor Q ₂ , while the base electrode of the latter transistor is connected _{to ground through a resistor R 4} which forms part of a base bias circuit for transistor Q ₂ . The collector electrode of the transistor Q ₂ is connected through a load _{resistor R 5} to the supply current voltage terminal 3 and also connected to an output terminal 2, from which an output signal E. is derived.

In the operating state of the above-described circuit according to FIG. 1, the transistor Q _{1 is} , when the voltage of the input signal E. is below a predetermined first threshold level or threshold value, which is described below, non-conductive or is in its switched-off state, while the transistor Q ₂ is conductive or is in its switched-on state. When the transistors Q ₁ and Q _{2 are} in their off and on states, respectively, the base voltage V, _{2 of} the transistor Q _{2 is} approximated by the equation

^V b2 I ^V cc ~ ^(I)

bestüurt, where r-, r _g and r ^ are the resistance _{values of the resistors R 1} and R ₃ and R ₄ , respectively.

When the transistors Q ₁ and Q ₂ are switched off in their

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is activated or switched on, the Voltage of the output signal £. derived from the output terminal 2 by the following equation certainly:

_{E =} ν out ^v cc

where r ₂ and r _{g are} the resistance values of the resistors or R ₅ are as PY ₃₆₂ ^ ^{d e} base-emitter voltage of the transistor Q _2.

When transistor Q _{2 is} in an on state, the voltage at junction J, where the emitter electrodes of transistors Q ^ and Q _{2 are} connected to resistor R ₂ , is equal to Vj ₁₂ - Vj ₃₀₂ (where ^V be2 ^d * ^{e Bas} i ⁸ " ^Em ^ ' ^trter ' ~ ^s P ^annun g ^ ⁸ transistor Q ₂ ). Thus, the transistor Q- is switched from its off state to its on state only when the voltage V ^ ₁ , which is applied to its base electrode by the input signal E ^ _n , is at least equal to a first threshold voltage Vj-, which is determined as follows:

u -V - V «. V + V

bl ^v thl " ^v b2 ^v be2 ^v bel

where V.ο-j is the base-emitter voltage of transistor Q ^ is.

Since it can be assumed that V, _e , and V. _{2 are} equal, and given Equation (I) above, Equation (III) can be rewritten as follows:

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^v th-i

When the transistor Q _{1 is} switched on, the transistor Q "is switched off, the base voltage ^V 'b2 of ^the T * ¹³¹ ^ ⁸ * ⁰ * ¹⁸ Q ₂ then being determined as follows:

v _b2

where I. is the current which flows through the resistors R and R ₁ ^ to earth.

It can also be seen that when the transistor Q _{2 is} in its off state and the transistor Q ^ is in its on state, the situation is as follows:

where I is the collector current of transistor Q ^. Equation (VI) can be rewritten as follows:

I = ^V cc * ¹¹ I ¹ C
1 (VII)

If equation (VII) is substituted for I ₁ in equation (V), equation (V) becomes as follows:

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As soon as the transistor Q _{1 is} in its switched-on state, it remains in this state until the voltage V, ^ applied to the base electrode of the transistor Q ^ by the input signal E. is lowered to or below _{a second welding voltage V th2,} which can be written as follows:

^V bl - < ^V th2 = ^V 'b2 - ^V be2 ^{+ V} bel

or

m 5 ^v h- * o = ^V cc ^r i · " ^r l ^r '4 ^I c
bl <th2 _— ^ ₅ -

When the transistor (L is in its switched-on state and the transistor Q _{2 is} in its switched-off state, the voltage at the output terminal 2 is only determined by the supply voltage V, ie:

^E out = ^V cc ^CXI)

When comparing equation (IV) and (X) above, it can be seen that the first welding voltage V ,, of the input signal at which transistor Q ^ switched from its off state to its on state and transistor Q ₂ from its switched on state State is switched to its off state by the amount ^r l H c _greater than the second threshold voltage V ^{th2 r} l ^{+ r} 3 ^{+ r> i} f of the input signal, at which the transistor Q ₁ from its on state to its off state is fed back while transistor Q _{2 is} from its off state

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is returned to its on state. Thus, the prior art circuit of Fig. 1 has a hysteresis property. A comparison of equations (II) and (XI) above shows that the output voltage at terminal 2 is smaller when transistor Q _{2 is} in its on state than when this transistor is in its off state.

In the known circuit described above with reference to FIG. 1, however, the operating voltage level of the input signal E. must be comparatively high, specifically as a result of the comparatively large voltage drop from the common emitter resistor R ₃ . From the equations (IV) and (X) is further seen that the first and second threshold voltages V, and V ₂ on the values ^v r ,, r 'and r ,, resistors R ,. R ₃ and R ^ are dependent, it can be seen from equations (II) and (XI) that the difference or range of the change in the output circuit of the circuit for the switched-on or switched-off state of the transistor Q _{2 is} also partly dependent on the resistance values r ^, T ₃ and r ^ is dependent. Thus, the difference between the threshold voltages VJ ₁₁ and V _th2 cannot be interpreted independently of the range of the change in the output signal voltage. If the working level of the input signal voltage does not have to be excessive and if a sufficiently large difference between the threshold voltages V ^ ₁ and Vj- has to be provided in order to obtain a suitable hysteresis property, only a relatively narrow or small change in the output signal voltage can in fact E. can be obtained. It has been found that at a supply voltage V of 12 volts, the maximum range of the change in the output signal voltage is approximately

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or 3 volts, that is, E _Qut in equation (XI) is 12 volts while E _{Q ±} in equation (II) is about 9 or 10 volts. The relatively large voltage drop across the common emitter resistor R "is a further reason for the described narrow range of the change in the output signal voltage derived from the known circuit, such a narrow or small range of the change in the output signal voltage limiting the areas of application of the known circuit or circuit design problems with certain uses the same results.

Referring now to FIG. 2, this figure shows that the circuit according to the invention, as shown therein, comprises a first and a second transistor Qg and Q ₄ , each of which has a control or base electrode and a first and second electrode, such as collector or Emitter electrodes, as shown. The input signal E. is applied to an input terminal 1 which is connected through a resistor Rg to the base electrode of the transistor Q ₃ * The first or collector electrode of transistor Q ₃ is connected through a Belastungewiderstand R ₈ with a clamp 3 which is a supply voltage ⁺ V receives from one side of a supply power source (not shown). The other side of the feed current source, which can be at ground or reference potential, is directly connected to the second or emitter electrodes of the two transistors Q ₃ and Q ₁ ^. The first or collector electrode of the transistor Q ₃ is also connected to an output terminal 2, from which the output signal E. is derived, wherein it is also connected to the S-fcuer or base electrode of the transistor Q _14, preferably through a resistor R _g , which is selected to cover the range of change in the output signal E. to

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control, as described below, and which can be omitted in theory. The control or base electrode of transistor Q ₃ is finally connected through a resistor to the first or H- Kollektorelektroäe of the transistor Q. ₃

In the operating state of the circuit according to the invention described above with reference to Pig »2, when the clamping ring of the input signal E ^ is below a predetermined first threshold level V i. J ₁₁ is, as described below, the transistor Q _{3 is} non-conductive or is in its switched-off state, while the transistor Q ₁ ^ is conductive or is in its switched-on state. .. The first threshold level V, the Eingängssignals E ^ _n, is at which the transistor _Q3 is switched or switched from its off state to its on-state, is approximately determined by the following equation:

E _in * V _thl = Vi V ₁₃₆₃ --- (XII)

r ₇

where r _g and r- are the resistance values of resistors R _β and R ₇ , respectively, and Vj _{363 is} the base-emitter voltage of transistor Q ₃ .

When the voltage of the input signal E. to the first threshold level V ... or above, transistor Q _{3 is} turned on to create a conductive path between its collector and emitter electrodes, while transistor Q ₁ ^ is turned off. Since there is only a very small voltage drop in the conductive path between the collector and emitter electrodes of the transistor Q ₀ , the voltage of the output signal E. nearly

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determined by the following equation:

^E out = ^V oe3 = 0

where V _{3 is} the collector-emitter voltage of transistor Q ₃ .

When the transistor Q _{3 is} in its on state and the transistor Q _{1+ is} in its off state, the base voltage of the transistor Q _{3 is} approximately equal to the voltage of the input signal E. Accordingly, the transistor Q _a remains in its switched-on state, while the transistor Q ₁ remains in its switched-off state until the voltage of the input signal E. has fallen to a second threshold voltage level V._ «, which is approximately determined by the following equation :

^E in I ^V th2 Γ ^V be3 ^(XIV >

When the voltage of the input signal E. drops to the second threshold voltage level V., "or below, the transistor Q _{3 is switched} to its switched-off state and the transistor Q ₁₊ to its switched-on state, ie the circuit is returned to its original state, where the voltage of the output signal E _{Qut is} determined by one or the other of the following equations (XV) and (XVI):

(a) If resistor R _{g has} a terminal resistance other than zero, then

^E out

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where r _ß and r _g are the resistance values of the resistors Rg and Rg, respectively, and Vj ₃₆ ^ is the base-emitter voltage of the transistor Q ₁ ^; or

(b) If the resistance value r _{g of} the resistor R _{g is} zero, ie if the resistor R _g is omitted from the circuit, then

< ^XVI)

A comparison of equations (XII) and (XIV) shows that the circuit according to the invention has a hysteresis property, ie that the first threshold voltage level V. _hl , at which the transistor Q _{3 is switched} from its switched off to its switched on state, by the value ^r 6 ^ ^r 7 »^ be3 S ¹ ^ ⁸⁸⁶ ** as the second threshold voltage level V .. j of the input signal at which the transistor Q _{3 is switched} back from its switched-on state to its switched-off state. As can be seen from FIG. 3, if the voltage of the input signal E., which is applied to the circuit according to the invention, increases linearly during the period t to t ", as shown at A, and then during the period t" to t ^ , as shown at B, then decreases linearly, the transistor Q _{3 is} in its switched-off state in the time periods t to t- and t- to t _u , and in its switched-on state in the time period t ^ to t ₃ · in particular is during the period t to t ^ the voltage of the input signal E. below the first threshold voltage level V ^., the equation (XII), so that the transistor Q- is in its off state. In time t, the input signal reaches the first threshold voltage level ^V thl * ^wobe ^ - accordingly the transistor Q _{3 is switched} to its on state. The

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Transistor Q ₃ in its switched-on state, while the voltage of the input signal increases in the time span t 1 to ± 2 and then decreases in the time span tg to t _g , the voltage of the input signal still being above the second threshold voltage Vj- of the equation in the last-mentioned time span (XIV) lies. In the time t ₃ , the voltage of the input signal drops to the second threshold voltage level, so that the transistor Q _{3 is} then switched to its switched off state, in which it _{remains during the time period t 3 to t 1 of} the further decreasing input signal voltage.

If the voltage of the input signal E. is repeatedly increased and decreased linearly, as for example at A and B in Fig. 3, then the position of the output signal voltage ^E out ^relat: * - ^{v to the} input signal voltage E ^ _{n forms} a hysteresis loop or curve, as shown in Fig. Ί, where the designations t, t ,, t “t * - and t ^ correspond to the similarly designated times in FIG. From Fig. H it can be seen that the output signal voltage has the value ^r 9

ccbe during the time period t to t, and ^r 8 ^{+ r} 9 t ₃ to t ^ and has the value zero during the time period t- ^ to t ₃ . If the resistor R _g is omitted from the circuit or has a resistance value of zero, then of course the output voltage has the value V _{bed during the time periods t Q} to t ₁ and t _g to t 1, as shown in the above equation (XVI).

It should be noted here that in the transistor circuit according to the invention, as shown in FIG. 2, those described above Disadvantages of the circuit of FIG. 1 according to the prior art can be avoided as follows:

Since the emitter electrodes of the transistors Q ₃ and Q ^ are connected directly to ground, the level of the input

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signal voltage E. be relatively low.

Since the difference between the first and second threshold voltage levels V. ^, and VJ _{12 of} the input signal E ^ _{n is} determined by the resistance values r _ß and r _? of the resistor R or R ₇ and the base-emitter voltage of the transit ports used is determined, as achieved from equations (XII) and XIV), and since the range of the change in the output signal voltage E is determined by the resistance values Vg and Vg of the resistors Rg and R _g , the supply voltage V and the base-emitter voltage of the

CC

applied transistors is determined, as can be seen from equations (XIII) and (XV), the difference between the threshold voltage levels V,, and V., “independent of the range of the change in the output signal voltage.

The range of change in the output signal voltage, that is, the difference between the values of the output signal voltage as obtained from equations (XIII) and (XV), can also be made relatively large and almost equal to the value of the supply current voltage V by changing the resistance value r _g des Resistance R _g is selected accordingly.

The transistor circuit according to the invention is also advantageous in that it consists of a minimum number of components, ie only two transistors and a maximum of four resistors including the resistor R _g . Since the circuit does not contain reactive elements, it is particularly suitable to be formed as an integrated circuit.

In a specific practical example of an invented

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Proper circuit, its components have the following values:

R _c = t.3k Λ
b

R ₇ = 3.9 k XL
R ₀ = 10 k Λ
R ₉ = 200 JX

V _cc = 12 V.

Referring now to FIG. 5, this figure shows that the transistor circuit according to the invention is used as a color killer signaling circuit 24 can be used advantageously in a color television receiver. As shown, the Color television receiver an antenna 11 and an antenna tuner 12 for amplification of the RF signals received by antenna 11 and for conversion the RF signals in IF signals, which in an IF amplifier 13 are amplified. A video detector circuit IU is provided in order to obtain television signal mixtures from the output of the IF amplifier 13, the luminance and color difference components of these composite television signals through a luminance channel 15 and a color difference amplifier, respectively be selected or reinforced.

A deflection and synchronization circuit 17 separates synchronizing signals from the mixed signals, which by the Video detector 14 are selected and generates line or horizontal and vertical deflection signals which the clamps X and Y of a color cathode ray tube 27 are supplied. The circuit 17 also generates line gate signals which a color synchronizing signal separating circuit 18 are supplied, to control the gate control of the latter, through which color sync signals are separated from chrominance signals,

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which are received by circuit 18 from color difference or chrominance amplifier 16. A color sync overshoot circuit 19 sets the out of the burst signal separation circuit 18 received intermittent bursts into continuous bursts, which are fed to a carrier wave oscillator 20, which is a carrier wave with its frequency of 3.58 MHz, which in phase and frequency with the continuous color sync signals from the overshoot circuit 19 are locked.

The continuous color sync signals from the harmonic circuit 19 are also fed to a color sync detector circuit 21, which determines the average level of the continuous color sync signals and generates a corresponding direct current output signal, which is amplified in a direct current amplifier 22. The amplified output of the amplifier 22 is fed as an input signal E. to the input terminal 1 of the transistor circuit according to the invention, whereby the color killer signal generator circuit 24 is formed. The output signal of the circuit 2H _9, which is derived from the output terminal 2 of the same, is fed as a color killer signal K to the chrominance amplifier 16 in order to render the latter ineffective, so that a monochromatic or monochromatic reproduction of the television picture is obtained when monochromatic television signals are passed through the antenna 11 received or when the output signals from the amplifier 22 are below the threshold voltage levels of the circuit 24, as described in detail below.

The output signals from the amplifier 2 2 are also fed to an automatic chrominance control circuit 2 3, which is the gain value of the chrominance amplifier 16 according to the level of the output signals from the

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stronger 22 controls. A color synchronous demodulator 25 demodulates Color difference signals from chrominance signals, which are supplied by the chrominance amplifier 16, by means of the carrier signal from the oscillator 20, where these color difference signals and luminance signals from the channel 15 are combined in a matrix circuit 26 to generate color component signals R, G and B, which are supplied to the respective cathodes of the color cathode ray tube 27.

The one consisting of the transistor circuit according to the invention Color killer signal generator circuit 24 may be implemented as an integrated circuit on a semiconductor die or as an integrated circuit a substrate or support that can also accommodate other circuits such as the chrominance amplifier circuit 16, oscillator circuit 20, color burst detector circuit 21, amplifier circuit 22 and the chrominance control circuit 2 3 and the like.

In the case of the color television receiver described, the color killer signal generator circuit 24 according to the invention operates as follows:.

If the level of the input signal voltage E. which is supplied to the terminal 1 of the circuit 24 and which corresponds to the level of the burst signals which are separated from the received television signals, is high enough to turn on the transistor Q ₃ , the output signal or color killer signal K a low level. This low level output signal from the circuit 24 makes the chrominance amplifier 16 effective so that color images are displayed by the color cathode ray tube 27. On the other hand, when the level of the input signal voltage E ^ _n supplied to the circuit 24 is applied.

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is sufficiently low to turn transistor Q ₃ off, the output signal K from circuit 24 has a high voltage level, thereby rendering the chrominance amplifier ineffective, so that monochromatic images are displayed by cathode ray tube 27.

Due to the above-described hysteresis property of the circuit which forms the color killer signal generator circuit 24, the level of the color burst signals at which the reproduced images change from monochromatic images to color images corresponds to the first threshold voltage level Vj- and is higher ^{by the value r} ß / ¹ ^ Vk ₆ as the level of the burst signals at which the reproduced images change from color images to monochromatic images, which corresponds to the second threshold voltage level V., 2. The hysteresis property of the color killer signal generator circuit 24 thus ensures that a stable Farbkxllerarbeitswexse is realized, ie that the Itaschaltung or the transition from the reproduction of color images to monochromatic images is not caused by small changes or fluctuations in the level of the color sync signals.

Although an embodiment of the present invention and. a desirable field of application of the same below With reference to the accompanying drawings described above in detail, the invention is understood not on this particular embodiment and this particular one Field of application limited, with various modifications and other uses within the scope of those skilled in the art the scope of protection of the attached claims can be selected.

Claims: 40981 5/1022

Claims (5)

Patent claims ^ Circuit with a first and a second transistor ^ sturgeon, each of which has a control electrode and first and second additional electrodes, between which a conductive path is formed when the transistor is switched on by applying a control voltage exceeding a predetermined value to the corresponding control electrode is applied, with input and output signal terminals receiving or supplying input and output signal? · voltages, and a voltage source is provided, the opposite sides of which are at different potentials, and electrical connections are provided between said transistors, terminals and the voltage source to to alternately switch on the first and the first transistor depending on the value of the input signal voltage with a hysteresis property and to change the output signal voltage depending on which of the transistors is switched on, characterized in that a first resistor (Rg ) the input terminal (1) with the control electrode of the first transistor (Q ₃ ), a second resistor (Rg) connects one side (3) of the voltage source with the first additional electrode of the first transistor (Q ₃ ), the first additional electrode of the first Transistor (Q ₉ ) is connected to the output signal terminal (3) and also to the control electrode of the second transistor (Q ₄ ), the second additional electrodes of the first and 409815/1022 of the second transistor (Q ₃ or Q ^) are connected to the other side (earth) of the voltage source, and that the control electrode of the first transistor (Q ₃ ) is connected to the first additional electrode of the second transistor (Q ₁₊ ). 2. A circuit according to claim 1, characterized in that the control electrode and said first and second additional electrodes of each transistor (Q ₃ and Q _1+, respectively) are base, collector and emitter electrodes. Circuit according to one of Claims 1 and 2, characterized in that said second additional electrodes of the first and second transistors (Q ₃ and Q _4, respectively) have low-resistance connections directly to the other side (earth) of the voltage source and that a resistor ( R-) is connected between the control electrode of the first transistor (Q ₃ ) and the first additional electrode of the second transistor (Q ^). Circuit according to one of the preceding claims, characterized in that a resistor (Rq) is connected between the first additional electrode of the first transistor (Q ₃ ) and the control electrode of the second transistor (Q ^>. 5. Circuit according to claims 3 and H, characterized thereby 409815/1022 shows that the first and the second transistor (Q ₃ or Q ^) and all resistors (R _ß> R ₇ , Rg and Rg) are formed as an integrated circuit on a single semiconductor wafer. The patent attorney 409815/1022 Blank page