Classifications

• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
  • G05F3/00—Non-retroactive systems for regulating electric variables by using an uncontrolled element, or an uncontrolled combination of elements, such element or such combination having self-regulating properties
  • G05F3/02—Regulating voltage or current
  • G05F3/08—Regulating voltage or current wherein the variable is DC
  • G05F3/10—Regulating voltage or current wherein the variable is DC using uncontrolled devices with non-linear characteristics
  • G05F3/16—Regulating voltage or current wherein the variable is DC using uncontrolled devices with non-linear characteristics being semiconductor devices
  • G05F3/20—Regulating voltage or current wherein the variable is DC using uncontrolled devices with non-linear characteristics being semiconductor devices using diode- transistor combinations
  • G05F3/24—Regulating voltage or current wherein the variable is DC using uncontrolled devices with non-linear characteristics being semiconductor devices using diode- transistor combinations wherein the transistors are of the field-effect type only
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
  • G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
  • G05F1/10—Regulating voltage or current 
  • G05F1/46—Regulating voltage or current  wherein the variable actually regulated by the final control device is DC
  • G05F1/56—Regulating voltage or current  wherein the variable actually regulated by the final control device is DC using semiconductor devices in series with the load as final control devices
  • G05F1/561—Voltage to current converters

Definitions

• the present invention relates to a transducer including an amplifier having a first input as well as an output coupled to a second input via a negative feedback loop and such that the voltage at said second input is substantially equal to an input voltage applied to said first input.
• Such a transducer is well known in the art, e.g. from the article "A Bipolar Voltage-Controlled Tunable Filter” by K. Fukahori, Journal of Solid-state Circuits, Vol. SC-16, No 6, December 1981, pp 729-731 and more particularly from Fig.8 on page 773 thereof.
• This transducer is able to convert an input voltage, e.g. a reference DC voltage, into a reference DC current flowing from the output.
• An object of the present invention is to provide a transducer of the above type, but which provides two separate output voltages that are respectively smaller and larger than said input voltage by accurate predetermined voltages.
• Such output voltages may for instance be used as reference voltages in the feedback loop of a sigma-delta modulator of the type disclosed in the published European patent application No 0155061.
• this object is achieved due to the fact that said output is coupled to a DC bias potential through three impedances in series, the junction between the first and the second being coupled to said second input and the junction between the second and the third constituting an additional output for said transducer.
• Fig. 1 is a schematic diagram of a first embodiment of a transducer according to the present invention
• Fig. 2 shows a second embodiment of a transducer according to the present invention.
• the transducer shown in Fig. 1 is built up by means of PMOS transistors PI to P3, of which P2 is connected in diode configuration, NMOS transistors Nl and N2, constant current source CS, resistors Rl to R3 and capacitor C.
• the transducer comprises an amplifier constituted by the cascade connection of a differential input stage DIS and an output stage OS and has an external input II and two external outputs 01 and 02.
• the differential input stage DIS comprises two parallel branches connected in series with the constant current source CS between the poles of a DC supply source. These poles are at the bias potentials V and ground respectively. These branches comprise the series connected transistors PI, Nl and P2, N2 respectively. The gates of transistors Nl and N2 constitute the negative and positive inputs II and 12 of the differential stage DIS, whilst the junction point of transistors PI and Nl is the output 03 of this stage.
• the output stage OS comprises the series connection, between V and ground, of transistor P3 and the resistors Rl to R3 which constitute the drain impedance of this transistor.
• the gate of transistor P3 is controlled by the output 03 of the input stage DIS and the drain of this transistor P3 constitutes the transducer output 01.
• the latter is connected to the output 03 via capacitor C which is used for stability purposes as well as to the input 12 of the input stage stage DIS via the feedback resistance Rl.
• 12 is the feedback input of DIS.
• the junction point of the resistors R2 and R3 is the transducer output 02.
• resistors Rl/3 of the output stage OS may also be connected as represented in Fig. 2. Therein they constitute the source resistance of transistor P3 whose gate is again controlled by the output 03 of the differential input stage DIS. However, II and 12 are now used as feedback input and as external input of the transducer respectively. In both cases the external input is at a high impedance level and the three resistances Rl/3 are decoupled therefrom.
• the output 01 is connected to the positive input 12 via feedback resistor Rl because the voltages at 03 and 01 vary in opposite direction.
• the output 01 is connected to the negative input II via resistor Rl because these voltages vary in the same direction.
• V01 VI + Rl.I C2)
• V02 VI - R2.I C3) or, when taking the relation CD into account by
• V01 VI + V1.R1/CR2+R3) C )
• V02 VI - V1.R2/CR2+R3) C5)
• V01 VI - CV-VDR1/CR2+R3) C6)
• V02 VI + CV-VDR2/CR2+R3) C7)

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• General Physics & Mathematics (AREA)
• Radar, Positioning & Navigation (AREA)
• Automation & Control Theory (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Nonlinear Science (AREA)
• Amplifiers (AREA)

Applications Claiming Priority (1)

Publications (1)

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• 1988
  • 1988-12-05 EP EP19890900595 patent/EP0398897A1/de not_active Withdrawn
  • 1988-12-05 WO PCT/EP1988/001129 patent/WO1990006547A1/en not_active Ceased
• 1989
  • 1989-11-21 AU AU45327/89A patent/AU625696B2/en not_active Ceased

Non-Patent Citations (1)

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