US 5,313,113 AGranted

Sample and hold circuit with full signal modulation compensation using bipolar transistors of single conductivity type

AssigneeHughes Aircraft Company

InventorLloyd F. Linder

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Abstract

A diode bridge (12) includes a plurality of diodes (D1,D2,D3,D4) for coupling an input voltage signal (Vin) through a resistor (RH) to a holding capacitor (CH) for sampling when the diodes (D1,D2,D3,D4) are forward biased, and uncoupling the voltage signal (Vin) from the capacitor (CH) for holding when the diodes (D1,D2,D3,D4) are reverse biased. A constant current drain (S1) causes a constant bias current (IBIAS) to flow out of the bridge (12) through first and second bias current nodes (N1,N2) to a voltage source (VEE). The nodes (N1,N2) are also connected through current source resistors (R1,R2) to a voltage source (VCC). A first current regulator (72) is bootstrapped to the input signal (Vin) and regulates first and second bias currents flowing into the nodes (N1,N2) to constant values (IBIAS/2) to compensate for resistive current source modulation. A second current regulator (92) is also bootstrapped to the input signal (Vin) and regulates bias current flowing through the resistor (RH) into the junction (20) between the resistor (RH) and the capacitor (CH) to a constant value (IBIAS/4) to compensate for output slew current modulation.

Claims30

Dependent claims

A sample and hold circuit, comprising:

voltage holding means;
diode bridge means having an input for receiving a voltage signal, an output connected in circuit to the holding means, a first bias current node and a second bias current node;
current drain means for causing a predetermined constant bias current to flow out of the bridge means;
first current source means for supplying a first bias current into the first node;
second current source means for supplying a second bias current into the second node;
switch means for selectively connecting the first node to the drain means and disconnecting the second node from the drain means, thereby biasing the bridge means for coupling the input to the output for sampling;
or connecting the second node to the drain means and disconnecting the first node form the drain means, thereby biasing the bridge means for uncoupling the input from the output for holding;
and
current regulator means responsive to the voltage signal for regulating at least one of said first and second bias currents to predetermined first and second constant values respectively in response to variation of the voltage signal;
in which
the first current source means comprises a first resistor connected between the first node and a voltage source means;
the second current source means comprises a second resistor connected between the second node and the voltage source means;
and
the current regulator means comprises:
transistor means having a current circuit and a control terminal, with said current circuit connected to induce respective currents through the first and second resistors;
and
control means responsive to the voltage signal for applying a control signal to the transistor means' control terminal to adjustably control the current flow through the transistor means' current circuit and thereby regulate said first and second bias currents to said first and second constant values respectively.

14 more elements

A sample and hold circuit, comprising:

voltage holding means;
diode bridge means having an input for receiving a voltage signal, an output connected in circuit to the holding means, a first bias current node and a second bias current node, said holding means comprising a resistor and a capacitor connected in series across the output of the bridge means;
current drain means for causing a predetermined constant bias current to flow out of the bridge means;
first current source means for supplying a first bias current into the first node;
second current source means for supplying a second bias current into the second node;
switch means for selectively connecting the first node to the drain means and disconnecting the second node from the drain means, thereby biasing the bridge means for coupling the input to the output for sampling;
or connecting the second node to the drain means and disconnecting the first node from the drain means, thereby biasing the bridge means for uncoupling the input from the output for holding;
and
current regulator means responsive to the voltage signal for regulating at least one of said first and second bias currents and the current flowing through said resistor to predetermined first, second and third constant values respectively in response to variation of the voltage signal;
in which
said resistor and said capacitor define a junction therebetween;
and
the current regulator means comprises;
third current source means connected to said junction;
and
control means responsive to the voltage signal for adjustably controlling current flow through the third current source means and thereby regulating said current flowing through said resistor to said third constant value.

13 more elements

A sample and hold circuit, comprising:

voltage holding means;
switchable diode bridge means having an input for receiving a voltage signal, an output connected to supply a current to the holding means, a first bias current node through which a first bias current flows and a second bias current node through which a second bias current flows;
current regulator means for bootstrapping to the voltage signal at least one of said first and second bias currents and said current supplied from the diode bridge means output to the holding means, and thereby maintaining said first and second bias currents and said current supplied to the holding means at predetermined first, second and third constant values respectively;
a first current source resistor connected in circuit between the first node and a voltage source means;
and
a second current source resistor connected in circuit between the second node and the voltage source means;
in which the current regulator means comprises:
transistor means having a current circuit and a control terminal, with said current circuit connected to induce respective currents through the first and second resistors;
and
control means responsive to the voltage signal for applying a control signal to the transistor means' control terminal to adjustably control the current flow through the transistor means' current circuit and thereby regulate said first and second bias currents to said first and second constant values respectively.

7 more elements

A sample and hold circuit, comprising:

voltage holding means;
switchable diode bridge means having an input for receiving a voltage signal, an output connected to supply a current to the holding means, a first bias current node through which a first bias current flows and a second bias current node through which a second bias current flows;
and
current regulator means for bootstrapping at least one of said first and second bias currents and said current supplied from the diode bridge means output to the holding means to the voltage signal, and thereby maintaining said first and second bias currents and said current supplied to the holding means at predetermined first, second and third constant values respectively;
said holding means comprising a resistor and a capacitor which are connected in series across the output of the bridge means and define a junction therebetween;
and
said current regulator means comprising:
third current source means connected to said junction;
and
control means for adjustable controlling current flow through the third current source means and thereby regulating said current flowing through said resistor to said third constant value.

7 more elements

Dependencies are inferred from the claim text.