US3798468A - Analog voltage switch - Google Patents

Analog voltage switch Download PDF

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Publication number
US3798468A
US3798468A US00308926A US3798468DA US3798468A US 3798468 A US3798468 A US 3798468A US 00308926 A US00308926 A US 00308926A US 3798468D A US3798468D A US 3798468DA US 3798468 A US3798468 A US 3798468A
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United States
Prior art keywords
transistor
analog voltage
emitter
base
transistors
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Expired - Lifetime
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US00308926A
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English (en)
Inventor
K Elshuber
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Texas Instruments Inc
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Texas Instruments Inc
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Publication date
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/14—Modifications for compensating variations of physical values, e.g. of temperature
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/72—Gated amplifiers, i.e. amplifiers which are rendered operative or inoperative by means of a control signal
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
    • H03K17/56—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices
    • H03K17/60—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being bipolar transistors
    • H03K17/62—Switching arrangements with several input- output-terminals, e.g. multiplexers, distributors
    • H03K17/6257—Switching arrangements with several input- output-terminals, e.g. multiplexers, distributors with several inputs only combined with selecting means

Definitions

  • the analog voltage switch employs primarily semiconductor components and is especially applicable to use in an integrated form in that current amplifications of complementary semiconductor components and forward voltages of diodes employed in the analog voltage switch are of substantially the same magnitude and constant current sources included therein supply substantially the same current.
  • the temperature-dependent deviations of the semiconductor components employed in the analog voltage switch effectively cancel out each other such that the circuit comprising the analog voltage switch is substantially independent of temperature.
  • This invention relates to an analog voltage switch comprising a plurality of channels which each have an analog voltage input and 'a control input for selecting the channel, and an analog voltage output at which the analog voltage fed to the analog voltage input of the selected channel appears.
  • a requirement of such analog voltage switches is that the analog voltage appearing at the analog voltage output reproduces as exactly as possible the analog voltage supplied to the selected channel.
  • This requirement is, however, particularly difficult to meet when the'analog voltage switch is constructed with semiconductor circuit elements, especially in integrated form. In this case, errors arise in the transmission of the analog voltage from the selected input to theoutput, due in particular to the temperature dependence of the semiconductor circuit elements.
  • the problem underlying the invention is the provision of an analog voltage switch with small input current, low temperature drift and low output impedance which is particularly suitable for construttion in the form of an integrated circuit.
  • each channel contains a transistor whose emittercollector path is connected on the one hand to ground and on the other, via a constant current source to the first pole of a voltage source whose second pole isconnected to ground, that the junction between transistor and constant current source of each channel is connected via a decoupling diode to the base of an output transistor which is complementary to the transistors of the channels and the emitter-collector path of which is connected on the one hand to the first pole of the voltage source and on the other via a constant current source to ground, that the analog voltage input of each channel is connected to the base of the transistor via a diode, and that there is connected in parallel with the emitter-collector path of the transistor of each channel a controllable switch whose control input is connected to the control input of the channel.
  • the transistors of the unselected channels are short-circuited by the parallel-connected switches.
  • the switch of the selected channel is open so that its transistor is connected in series with a constant current source to the voltage source and controls the complementary output transistor which in turn is connected in series with a constant current source to the voltage source.
  • the input voltage is also applied to the base of the transistor of the selected channel via a diode.
  • the latter may be so designed that the current amplifications of the com plementary transistors and the forward voltage of the diodes are of substantially the same magnitude and the two constant current sources supply substantially the same current.
  • controllable switch in each channel is formed by a second transistor which is complementary to the first transistor and connected in parallel therewith and the base of which is connected to the control input.
  • FIG. 1 shows the basic circuit diagram of an analog voltage switch according to the invention having two channels
  • FIG. 2 is a more detailed circuit diagram of an analog voltage switch according to the invention having four channels, and
  • FIG. 3 is a schematic circuit diagram for explaining the mode of operation.
  • the analog voltage switch illustrated in FIG. 1 contains in the first channel two complementary transistors T11 and T12 which are connected in parallel to each other in such a manner that the collector of the pnp transistor T11 and the emitter of the npn transistor T12 are connected to ground.
  • the emitter of the pnp transistor T11 and the collector of the npn transistor T12 are connected on the one hand by a constant current source Q11 to a terminal K1 to which the positive pole of a DC voltage source is connected whose negative pole is grounded; on the other hand they are connected via a diode D12 to the base of an output transistor T1.
  • the collector of the output transistor T1 is connected to the terminal Kl while its emitter is connected via a constant current source 01 to ground. Connected to the emitter is the output terminal A1 of the analog voltage switch.
  • the base of the transistor T11 is connected via a diode D11 to an input terminal E11 to which the analog voltage of the channel 1 is applied.
  • the base of the transistor T12 is connected to a terminal E12 to which is fed the control signal for the channel 1.
  • the channel 2 is constructed in identical manner as the channel 1 from the circuit elements T21, T22, E21, E33, D21, D22 and Q21.
  • the diodes D12 and D22 serve for mutual decoupling of the channels.
  • the non-conductive transistor T12 has been omitted because its impedance can be considered to be infinitely large.
  • the channel 2 is also omitted because it is completely disconnected by the decoupling diode D22.
  • the emitter of the transistor T11 assumes the following voltage:
  • the output voltage U A corresponds exactly to the input voltage U if firstly the forward voltages of the diodes D11 and D12 are of the same magnitude and secondly the pnp transistor T11 and the npn transistor T1 have the same current amplification. This can easily be achieved with integrated construction of the circuit.
  • the temperature drift of the diode D11 will be compensated by that of the diode D12 and the temperature drift of the transistor T11 by that of the transistor T1.
  • FIG. 2 shows a more exact circuit diagram of an analog voltage switch constructed according to this principle and comprising four channels.
  • the channels 1 and 2 consist of the same circuit elements as in FIG. 1; the only difference is that a resistor R12 is inserted in the connection between the input terminal E12 and the base of the transistor T12 and a resistor R22 is inserted in the connection between the input terminal E22 and the base of the transistor T22.
  • the channels 3 and 4 are made up in similar manner from the circuit elements T31, T32, E31, E32, D31, D32, R32, and T41, T42, E41, E42, D41, D42 and R42.
  • the constant current source of the transistor T1 is formed by an npn transistor T2 to whose base a constant voltage is applied from a voltage divider which is connected between the DC voltage terminal K1 and ground and consists of a pnp transistor T3 and an npn transistor T4 connected as diode by shorting the basecollector junction.
  • the constant current source of each channel is formed by a pnp transistor T13, T23, T33 or T43 to whose base is applied a constant voltage.
  • This constant voltage for the bases of these transistors is supplied by a common voltage divider connected between the DC voltage terminal K1 and ground and consisting of the series circuit of a pnp transistor T5 connected as diode, an npn transistor T6 and a resistor R1.
  • This voltage divider also supplies the base bias for the transistor T3.
  • the base bias for the transistor T6 is supplied by a voltage divider which is formed by the series connection of two resistors R2 and R3 and a transistor T7 connected as diode.
  • the entire circuit consists solely of transistors, diodes and resistors and it is therefore ideally suited for construction as an integrated semiconductor circuit. 7
  • An analog voltage switch comprising:
  • each of said channels having:
  • a pair of transistors of complementary conductivity types each having a collector, base and emitter; a common connection between the emitter of one of said pair of transistors and the collector of the other one of said pair of transistors; the collector of said one transistor and the emitter of said other transistor connected to a first reference potential; a constant current source for said channel comprising a third transistor having a collector, base and emitter, the collector-emitter path of said third transistor connected in series between a second reference voltage and said common connection of said pair of transistors; first means including a first diode connecting said analog voltage input to the base of a normally nonconductive one of said pair of transistors, said first diode being poled in the same direction as the base-emitter junction of said normally non-conductive transistor; second means connecting said control input to the base of a normally conductive one of said pair of transistors, and a second diode connected to said common connection of said pair of transistors and poled in an opposite direction from that of the
  • the said means for applying a constant bias to the base of each of said third transistors and to said fourth transistor comprises a first potential divider connected between said first and second reference potentials; said potential divider including a fifth transistor having a collector, base and emitter, the collector of said fifth transistor connected by a diode to said second reference potential, the emitter of said fifth transistor connected by a resistor to said first reference potential, and the base of said fifth transistor connected to a tap on a resistor-diode potential divider connected between said first and second reference potentials; the collector of said fifth transistor further being connected to the base of each of said third transistors to apply said constant bias thereto; a sixth transistor having a collector, base and emitter, the emitter-collector path of said sixth transistor connected to said second reference potential and by a third diode to said first reference potential, a junction between said third diode and said sixth transistor being connected to the base of said fourth transistor to supply said constant bias thereto.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Electronic Switches (AREA)
  • Amplifiers (AREA)
US00308926A 1972-01-18 1972-11-22 Analog voltage switch Expired - Lifetime US3798468A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2202250 1972-01-18

Publications (1)

Publication Number Publication Date
US3798468A true US3798468A (en) 1974-03-19

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ID=5833325

Family Applications (1)

Application Number Title Priority Date Filing Date
US00308926A Expired - Lifetime US3798468A (en) 1972-01-18 1972-11-22 Analog voltage switch

Country Status (12)

Country Link
US (1) US3798468A (sv)
JP (1) JPS49106273A (sv)
AT (1) AT327292B (sv)
BE (1) BE793546A (sv)
DE (1) DE2202250C2 (sv)
DK (1) DK132780C (sv)
ES (1) ES410711A1 (sv)
FR (1) FR2168390B1 (sv)
GB (1) GB1409918A (sv)
IT (1) IT976913B (sv)
NL (1) NL7300129A (sv)
SE (1) SE388987B (sv)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4829202A (en) * 1986-09-04 1989-05-09 Pilkington Micro-Electronics Limited Semiconductor integrated bipolar switching circuit for controlling passage of signals
EP0334545A3 (en) * 1988-03-22 1990-05-16 Texas Instruments Incorporated Single-level multiplexer
EP0938186A1 (en) * 1998-02-19 1999-08-25 STMicroelectronics S.r.l. Switching of a capacitor on a mutually exclusive selected one of a plurality of integrated amplifiers

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS54145469A (en) * 1978-05-06 1979-11-13 Sanyo Electric Co Ltd Signal switching unit
JPS58127735U (ja) * 1982-02-23 1983-08-30 株式会社ケンウッド スイツチング回路
DE3807811A1 (de) * 1988-03-10 1989-09-21 Philips Patentverwaltung Schaltungsanordnung zum wahlweisen verbinden von signalquellen mit einer signalsenke

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3522450A (en) * 1966-07-14 1970-08-04 Int Standard Electric Corp Current amplifying scanning circuit
US3526785A (en) * 1966-03-24 1970-09-01 Kozponti Fiz Kutato Intezet Sampling amplifier having facilities for amplitude-to-time conversion

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4935143U (sv) * 1972-06-23 1974-03-28

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3526785A (en) * 1966-03-24 1970-09-01 Kozponti Fiz Kutato Intezet Sampling amplifier having facilities for amplitude-to-time conversion
US3522450A (en) * 1966-07-14 1970-08-04 Int Standard Electric Corp Current amplifying scanning circuit

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4829202A (en) * 1986-09-04 1989-05-09 Pilkington Micro-Electronics Limited Semiconductor integrated bipolar switching circuit for controlling passage of signals
EP0334545A3 (en) * 1988-03-22 1990-05-16 Texas Instruments Incorporated Single-level multiplexer
EP0938186A1 (en) * 1998-02-19 1999-08-25 STMicroelectronics S.r.l. Switching of a capacitor on a mutually exclusive selected one of a plurality of integrated amplifiers
US6093981A (en) * 1998-02-19 2000-07-25 Stmicroelectronics S.R.L. Switching of a capacitor on a mutually exclusive selected one of a plurality of integrated amplifiers

Also Published As

Publication number Publication date
DK132780B (da) 1976-02-02
IT976913B (it) 1974-09-10
BE793546A (fr) 1973-04-16
FR2168390B1 (sv) 1978-06-02
GB1409918A (en) 1975-10-15
SE388987B (sv) 1976-10-18
NL7300129A (sv) 1973-07-20
ES410711A1 (es) 1976-01-01
DK132780C (da) 1976-07-05
JPS49106273A (sv) 1974-10-08
DE2202250B1 (de) 1973-02-01
AT327292B (de) 1976-01-26
ATA38173A (de) 1975-04-15
FR2168390A1 (sv) 1973-08-31
DE2202250C2 (de) 1975-11-20

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