Current-mode sinusoidal oscillator using single current amplifier
View Patent ↗A current mode sinusoidal oscillator includes a current amplifier with distinct current input and four output terminals. The amplifier includes a current input terminal X, a first and a second negative current feedback terminals I fo1 and I fo2 , along with a positive current output terminal I op and a negative current output terminal I on . The oscillator is characterized by a first feedback path that transmits a portion of a current at the first negative current feedback terminal I fo1 to the current input terminal X of the oscillator. Additionally, a second feedback path, interlinking I fo2 and X, comprises a three-stage phase lag network designed to confer a phase shift of negative 180 degrees to the current signal at a frequency of oscillation determined by capacitor and resistor values of the three-stage phase lag network. A load is connected between I op and I on , which receives the sinusoidal current at the frequency of oscillation.
1 . A current mode sinusoidal oscillator, comprising:
a current amplifier having a current input terminal X, a first negative current feedback terminal I fo1 , a second negative current feedback terminal I fo2 , a positive current output terminal I op and a negative current output terminal I on ;
a first feedback path connected between the first negative current feedback terminal I fo1 and the input terminal X, wherein the first feedback path is configured to transmit a portion of a current at the first negative current feedback terminal I fo1 to the current input terminal X;
a second feedback path connected between the second negative current feedback terminal I fo2 and the input terminal X, wherein the second feedback path is a three stage phase lag network configured to shift the phase of the current in the second feedback path by a negative 180 degrees with respect to the input current at a frequency of oscillation; and
a load connected between the positive current output terminal I op and the negative current output terminal I on , wherein an output current through the load is sinusoidal.
2 . The current mode sinusoidal oscillator of claim 1 , wherein the first feedback path comprises:
a first leg including a first resistor R 1 connected between the first negative current feedback terminal I fo1 and the current input terminal X, and
a second leg comprising a second resistor R 2 connected between the first negative current feedback terminal I fo1 and a ground terminal.
3 . The current mode sinusoidal oscillator of claim 2 , wherein the second feedback path comprises:
a third resistor R 3 connected to the second negative current feedback terminal I fo2 ;
a fourth resistor R 4 connected in series with the third resistor R 3 ;
a fifth resistor R 5 connected in series with the fourth resistor R 4 , wherein the fifth resistor R 5 is connected to the input terminal X;
a first capacitor C 1 having a first terminal connected to the second negative current feedback terminal I fo2 and a second terminal connected to the ground terminal;
a second capacitor C 2 having a first terminal connected to a junction between the third resistor R 3 and the fourth resistor R 4 and having a second terminal connected to the ground terminal; and
a third capacitor C 3 having a first terminal connected to a junction between the fourth resistor R 3 and the fifth resistor R 4 and having a second terminal connected to the ground terminal.
4 . The current mode sinusoidal oscillator of claim 3 , wherein a condition of oscillation (CO) of the output current is given by:
(
1
+
R
1
R
2
)
=
29.
5 . The current mode sinusoidal oscillator of claim 3 , wherein the frequency of oscillation f 0 of the output current is given by:
f
o
=
6
2
π
RC
where R=R 3 =R 4 =R 5 and C=C 1 =C 2 =C 3 .
6 . The current mode sinusoidal oscillator of claim 5 , wherein the resistor R 1 is about 32 kΩ, the resistor R 2 is about 1 kΩ, R is about 2 kΩ and C is about 10 nF, R is about 2 KΩ and C is about 10 nF.
7 . The current mode sinusoidal oscillator of claim 1 , wherein the load is a biomedical stimulation device selected from a group comprising a nerve stimulator, an electrode stimulator, a defibrillator, a deep brain stimulator and a muscle stimulator.
8 . A current driver for biomedical stimulation, comprising:
a DC current source;
a switch connected to the DC current source, wherein the switch is configured to one of connect and disconnect the DC current;
a current amplifier having a current input terminal x connected to the switch, a first negative current feedback terminal I fo1 , a second negative current feedback terminal I fo2 , a positive current output terminal I op and a negative current output terminal I on ;
a first feedback path connected between the negative current feedback terminal I fo1 and the input terminal x, wherein the first feedback path is configured to transmit a portion of a current at the first negative current feedback terminal I fo1 to the current input terminal X;
a second feedback path connected between the second negative current feedback terminal I fo2 and the input terminal x, wherein the second feedback path is a three stage phase lag network configured to shift the phase of the current in the second feedback path by a negative 180 degrees at a frequency of oscillation with respect to the input current; and
a biomedical load connected between the positive current output terminal I op and the negative current output terminal I on , wherein an output current driven through the biomedical load is sinusoidal.
9 . The current driver of claim 8 , wherein the first feedback path comprises:
a first leg including a first resistor R 1 connected between the first negative current feedback terminal I fo1 and the current input terminal x, and
a second leg comprising a second resistor R 2 connected between the first negative current feedback terminal I fo1 and a ground terminal.
10 . The current driver of claim 9 , wherein the second feedback path comprises:
a third resistor R 3 connected to the second negative current feedback terminal I fo2 ;
a fourth resistor R 4 connected in series with the third resistor R 3 ;
a fifth resistor R 5 connected in series with the fourth resistor R 4 , wherein the fifth resistor R 5 is connected to the input terminal X;
a first capacitor C 1 having a first terminal connected to the second negative current feedback terminal I fo2 and having a second terminal connected to the ground terminal;
a second capacitor C 2 having a first terminal connected to a junction between the third resistor R 3 and the fourth resistor R 4 and having a second terminal connected to the ground terminal; and
a third capacitor C 3 having a first terminal connected to a junction between the fourth resistor R 3 and the fifth resistor R 4 and having a second terminal connected to the ground terminal.
11 . The current driver of claim 10 , wherein a condition of oscillation CO of the output current is given by:
(
1
+
R
1
R
2
)
=
29.
12 . The current driver of claim 11 , wherein the frequency of oscillation f 0 of the output current is given by:
f
o
=
6
2
π
RC
where R=R 3 =R 4 =R 5 and C=C 1 =C 2 =C 3 .
13 . The current driver of claim 11 , wherein the resistor R 1 is about 32 kΩ, the resistor R 2 is about 1 kΩ, R is about 2 kΩ and C is about 10 nF.
14 . The current driver of claim 8 , wherein the biomedical load is a biomedical stimulator selected from a group comprising a nerve stimulator, an electrode stimulator, a defibrillator, a deep brain stimulator and a muscle stimulator.
15 . A method for providing biomedical stimulation, comprising:
connecting a DC current source to an input terminal of a current mode sinusoidal oscillator;
switching, by a switch connected to the DC current source, the DC current source ON;
wherein the current mode sinusoidal oscillator includes a current amplifier having a current input terminal X connected to the switch, a first negative current feedback terminal I fo1 , a second negative current feedback terminal I fo2 , a positive current output terminal I op and a negative current output terminal I on ;
connecting a first feedback path between the first negative current feedback terminal I fo1 and the input terminal X, and transmitting a portion of a current at the first negative current feedback terminal I fo1 to the current input terminal X;
connecting a second feedback path between the second negative current feedback terminal I fo2 and the input terminal X, wherein the second feedback path is a three stage phase lag network configured to shift the phase of the current in the second feedback path by a negative 180 degrees with respect to the input current at a frequency of oscillation;
connecting a biomedical load between the positive current output terminal I op and the negative current output terminal I on ; and
driving a sinusoidal output current through the biomedical load.
16 . The method of claim 15 , wherein connecting the first feedback path comprises:
connecting a first leg including a first resistor R 1 between the first negative current feedback terminal I fo1 and the current input terminal X, and
connecting a second leg comprising a second resistor R 2 between the first negative current feedback terminal I fo1 and a ground terminal.
17 . The method of claim 16 , wherein connecting a second feedback path comprises:
connecting a third resistor R 3 to the second negative current feedback terminal I fo2 ;
connecting a fourth resistor R 4 in series with the third resistor R 3 ;
connecting a fifth resistor R 5 in series with the fourth resistor R 4 , wherein the fifth resistor R 5 is connected to the input terminal X;
connecting a first terminal of a first capacitor C 1 to the second negative current feedback terminal I fo2 and connecting a second terminal of the first capacitor C 1 to the ground terminal;
connecting a first terminal of a second capacitor C 2 to a junction between the third resistor R 3 and the fourth resistor R 4 and connecting a second terminal of the second capacitor C 2 to the ground terminal; and
connecting a first terminal of a third capacitor C 3 to a junction between the fourth resistor R 3 and the fifth resistor R 4 and connecting a first second of a third capacitor C 3 to the ground terminal.
18 . The method of claim 17 , further comprising:
selecting the resistance of the first resistor R 1 and the resistance of the second resistor R 2 such that a condition of oscillation CO of the output current is met, subject to the calculation given by:
(
1
+
R
1
R
2
)
=
29.
19 . The method of claim 18 , further comprising:
selecting the resistance of the resistors in the second feedback path and the capacitance of the capacitors in the second feedback path to provide a desired frequency of oscillation f 0 of the output current wherein:
f
o
=
6
2
π
RC
where R=R 3 =R 4 =R 5 and C=C 1 =C 2 =C 3 .
20 . The method of claim 19 , further comprising:
selecting the resistance of R 1 to be about 32 kΩ, the resistance of R 2 to be about 1 kΩ, the resistance of R to be about 2 kΩ and the capacitance of C to be about 10 nF.