SU1274150A1 - Transistor-transistor logic element - Google Patents

Description

The invention relates to a pulse technique and can be used in digital logic circuits when increased performance and noise immunity is required.

The aim of the invention is to increase the speed and noise immunity of a TTL element.

The drawing shows a schematic diagram of a TTL element using a npp transistor as an input element.

The TTL element contains an input element 1, the first output of which is connected to the input 2, the second output through the first and second resistors 3 and 4 connected in series to the power supply bus 5, and the third output terminal is connected to the base of the phase separation transistor 6 -p, the collector of which is connected via the third resistor 7 to the power bus 5 and to the base of the first output transistor 8 of the nrp type, the collector of which is connected via the fourth resistor 9 to the power bus 5, and the emitter through the diode 10 is connected to the output 1I and the collector of the second output transistor and 12, the emitter of which is connected to the common bus, and the base - to the emitter 6 and through the fifth resistor 13 - to the collector of the absorbing transistor 14 of the pnp type, the emitter of which is connected to the common bus, the base through the seventh resistor 15 - to the common bus and with the collector of the additional transistor 16, the base of which is connected to the emitter of the transistor 8, and the emitter through the sixth resistor 17 is connected to the connection point of resistors 3 and 4.

As a starting element in the proposed TTL element, in addition to a pp, a pp transistor, a Schottky diode, an i-0iH diode, can be used.

Consider the work of the proposed TTL-element, when as the input element1 turned on pnp transistor.

TTL-element works as follows.

A feedback circuit has been introduced into the TTL element circuit. This allows, when the element is turned on, to make a high resistance of the base circuit of the second output transistor 12, which accelerates the switching on of the element. Pr off the element of the reverse circuit

connection allows you to make low impedance the base circuit of the transistor 12, which accelerates the switching off of the element.

At the low voltage level of input 2 (logical O), transistor 1 is in saturation mode.

On the collector of the transistor 1 voltage level

UK. “And; + and ,, „,

where Up is the voltage of the logical O

input 2;

 the voltage drop of the collector-emitter of the input transistor 1 in the saturation mode.

The voltage level is not enough to turn on transistors 6 and 12, so they are turned off. Diode 10, transistor 8 included. Transistor 8 is in active mode. At output 11, a voltage level of logical 1 is set.

UBb, v "u ,, - - and,,

i

where is the voltage of the power source;

 - the fall of the voltage on the base-emitter junction of the switched on transistor; Ug is the voltage drop across the on diode.

Potential is established on the base of transistor 1

S, “+ bz-.

The values of the resistors 4.3 and 17 are chosen such that the potential at the emitter of the transistor 16 is less than at the base of the transistor 16. At the same time, the transistor 16 is closed. Therefore, the transistor 14 is also closed. There is no current through resistor 13.

A potential is established at the common connection point of resistors 3,4 and 17

IT - Ucc + Ua-e)., F..o ,,, and - -R- --g-RjHU ,, + U,)

 and

(one)

cTlG

where the potential is at the base of the transistor 16,., - U; (2)

 - voltage drop

the switched transition of the transistor 8; Ur (. Is the voltage on the power bus 5; Rj, R is the resistance of resistors 3 and 4. With a logic O, the input 2 tons of consumption is equal to the input current of logic O at the input, because in the absence of a load, the currents of the resistors 7 and 9 can be neglected. At a logic voltage O, the conditions (1) must be fulfilled at the input, which, taking into account (2), has the voltage Ucc-U.8. As the input voltage rises, the potential to the collector of transistor 1 increases. The transistor remains in saturation mode until until the potential on its collector n reaches the value of Transistor 16 is closed until the pot The base at its base will not be lower than the value (1) by the amount of voltage from the base-emitter junction opening. Therefore, when the input voltage increases to 2 UL-ken, the current does not flow to resistor 13, since transistor 14 is closed and The flat transfer characteristic in the range of input voltages of Urfa, i.e., and transistors 6 and 12 begin to switch simultaneously, the circuit has an improved transfer characteristic, therefore, noise immunity is improved in a state of logical O at the input. With a further increase in the input voltage and ,, - 2%, - and „„ The switching of the TTL-element occurs, the transistor 1 switches to the inverse active mode of operation. Transistors 6 and I2 go into saturation mode. The output 11 sets the low voltage level of the logical ne, where iadn is the collector emitter voltage of the transistor 12 in the saturation mode. 504 The potential on the base of the voltage 16 decreases to the value of, “+ and,” where Uj, o is the voltage drop on the on diode 10. The lowering of the potential leads to the switching on of the transistor 16, which goes into active mode. Turning on the transistor 16 causes the transistor 14 to turn on, a resistor 13 appears. Moreover, the smaller the value of resistor I3, the lower the base current of transistor 12 and the lower the degree of saturation of transistor 12. When turning on transistor 16 and the transition of transistor 1 the inverse mode at a common point of resistors 3, 4 and 17 sets a certain potential and. The current of the resistor 4 is equal to the sum of the currents of the resistors 3 and 17: IR IRH CU ,, - U) G, (U- (2U, + Uj)) G, + + (U- (U ,,, + and, +, )) G ,,, de G., G, G - conductivity of resistors 3,4 and 17; (2Ujj. + U) is the base potential of transistor 1 with a voltage of logical 1 at input 2; (+ i, n) potential at the emitter of transistor I6 with a voltage of logical 1 at input 2; Vf is the voltage drop at the junction of the base of the collector of transistor 1 in inverse mode. From (5) we determine the value of U: and §5LUcf J: Gii 2y4 iygj,) iG (y,) G. + GG ,, In order to ensure the switching of the transistor 16, it is necessary that in this mode between the potentials and and Uj the ratio was satisfied. and - uj and, e. the difference should suffice to include the euransient transition of the transistor 16, taking into account (4) and (6) the word (7), we write in the vice

51274150

(,.) l G Liyb "i-Ui t-yiLl., G, 7 V state of logical O at the output of logical 1 at the input of resistor 4 is equal to T - Uct Ucc Ujj + 2 ol RR and N where and is determined from ( 6), and should not exceed the current of a typical TTL element so as not to increase the consumed power. The current of the resistor 3 is equal to t and - (2 iae-) t RJ-D i where - the base current of the transistor The current of the resistor 7 is equal to T - Its; () . M t R where KB is the collector current of trans 6; |) - Potential on the collective e. transistor 6 in the mode of the pan; R-J is the resistance of the resistor. Since the current of the resistor 3 is with the base current of transistor 6, it should suffice to saturate the transistor 7. Condition P., 1.5, where p is the gain factor of the transistor 6; S is the minimum degree of saturation of the transistor 6. Taking into account (10) and (11), the condition is:.) P, U celly i li For logical 1, the resistor 17 at the input is determined from level 1 ... 1. , I - emitter current transistor S (6. F (8)

and., „+

Js Transistor 16 is in active mode. The collector current of the rignor 16 is equal to T - - 6 -Mb p + 1 P de p - gain factor of the pnp of the transistor 17. At present, the technology of manufacturing integrated circuits allows to obtain ppp transistors with sufficiently high gain factors. base current in active mode. Therefore, when turning on transistor 16, the main part of the emitter current of transistor 16 goes to the collector of transistor 16. Transistor 14 is turned on and must be in saturation mode, its base current is 8 and M6 Ri5 1 -Ufe-R15 R, s-current of resistor 15; is the resistance of the resistor 15, the current (16) must be sufficient for the use of transistor 14, and the collector current is equal to I K14 R, dGe and. - voltage drop across the base. - emitter of transistor 12 in saturation mode; -dip of collector-emitter voltage of transistor 14. Between the base and collector current of transistor 14, the ratio WP IK-S should be performed. The base current of output transistor 12 in the state of logical O at output I1 is I 1 -I RT and K-i1 DeG ,, 1, 1 are determined from (10), CLL - .. J (11), (17). The base current of the transistor 12 must. ensure the saturation of the output transistor 12, the transistor 8 in the state of logical O at output 1 is closed. Thus, in the state of logical 1 at input 2, the output I1 is set to logical O, the feedback is turned on, which leads to a decrease in the base saturation current of the output resistor 18, since the resistor 13 is chosen less than the value of The base circuit of the output transistor in the sample element. Consider the operation of a TTL element in a pulsed mode. When, in the state of logic O, the front of the input pulse arrives at input 2, then logic level 1 is set to input 2. Transistors 6 and 12 do not have time to turn on and the feedback resistor 17 does not turn on transistor 16. The entire current of the resistor 4 goes to turn on the transistor 6. Until the transistor 12 is turned on, at the common connection point of resistors 3,4 and 17, the potential is set to and.,) 42 and, +

and.) (). ,, (,)

G. Vs, r co. „And“ Through a low-resistance circuit resistor 13 - transistor 14 is quickly discharged from the base current of a saturated output transistor, the faster the smaller the value of resistor 13. The value of resistor 13 can be reduced unlimitedly provided that the output saturation remains the transistor 12 and the transistor 1. In this case, a decrease in the value of the resistor 13 does not affect the on-delay of the circuit. When transistor 12 is turned off, the potential at the base of transistor i 6 increases and the feedback is turned off. Thus, the proposed TTL element circuit improves the noise immunity of the circuit and, therefore, improves the circuit performance while maintaining the same power consumption of a typical TTL element. There are various options for organizing feedback. For example, the base of the transistor 16 can connect (21)

and,

Claims (1)

B1b 50 and ,, S The values of R must be chosen with regard to the implementation (20). While the feedback is not working, the current in the resistor 13 does not branch off and the entire current of the transistor 6 goes to turn on the output transistor 12. Thus, the circuit is turned on quickly. After turning on the output transistor, the feedback is turned on, the resistor 13 - current of transistor 14 starts flowing into the circuit. When in logical state 1 at input 2 the negative edge of the input pulse arrives, input voltage 2 sets the voltage level of logic O. Transistors 6 and 12 saturation is maintained for some time. The feedback remains switched on and for the base current of the transistor 12 the low-impedance circuit of the base current is maintained. Similarly to (6) at the common connection point of resistors 3, 4 and 17 it is established (while transistor 12 remains in contact) to the collector of output transistor 12, additional elements can be included in the collector and base circuit of transistor 16: resistor, diode, etc. For adjustment switch-on delay values, you can add an additional resistor between the collector of the transistor 14 and the common bus. The invention includes a TTL element containing a pnp type dissolving transistor, an input element, the outputs of which are connected respectively to the input of the element via the first and second series-connected resistors to the power bus and to the base of the phase separation transistor of the type pnp collector connected to the base of the first output transistor of the pnp type, and through the third resistor to the power bus, the collector of the first output transistor through the fourth 9 127415010 the resistor is connected to the power bus, the emitter is connected to the high voltage via the diode connected to the high voltage, the seventh resistor and the stroke and the collector of the second output is an additional transistor type pnp, of a pnp type transistor whose emitter emitter is connected to the second which is connected to the common bus, a5 pin of the sixth resistor, the base - with The base is connected to the emitter by the phase-emitter of the first output transistor and the first pickup, and the collector is connected to the base of the first resistor, the first output transistor and through the seventh the sixth resistor is connected to the point of the resistor - with a common bus, which the first and Btoporo10 are connected to the emitter of the dissolver resistors, a different transistor, the collector of which is connected, which, in order to increase quickly, is connected to the second terminal of the resistor.