The document discusses methods to reduce noise in precision 10 µA current sources and mirrors, focusing on techniques such as using high-gain amplifiers, chopper amplifiers, and RC filters. It also emphasizes the importance of calibration methods and trimming resistors in maintaining low noise levels. The author is G.S. Javed, a PhD and analog design manager at King Consultants.

1. Precision 10uA Current
Sources and Mirrors
G S Javed, PhD
Analog Design Manager
Founder, King Consultants Education
drgs.javed@gmail.com
@ConsultantsKing

2. V-to-I : Current References
V
V
Current References
Voltage Reference
Circuit
BGR Core
Vref

3. Precision Current Sources
[slau507.pdf, Texas Instruments]
Precision 5 uA
current source
Vref
IOUT = Vref / RSET
= 1/ 100K = 10uA

4. Noise in V-to-I for Current References/ Mirrors
V
V
Current References
Voltage Reference
Circuit
BGR Core
Vref
*
* *
Current
Noise
Voltage
Noise

5. Approach to reduce/cancel the noise
1. Reduce the noise at the source – BGR or external reference voltage.
2. Use a high gain, low input offset Error Amplifier for fast settling and low
noise.
3. Explore the use of Chopper Amplifier to reduce the flicker noise.
4. Use a (RC) filter to reduce the current noise, in the high side current sensing.
5. Use a (RC) filter in the gate of the current mirror, to reduce the gate noise
voltage.
6. Use trimming resistors / digital controls – less expensive in current
technology.
7. Calibration methods for the same

6. Noise in Current Mirrors
1. Add RC filter to reduce the variations in the voltage and acts like a LPF.
2. It effectively reduces the impact of the gate noise and flicker noise.
[Razavi]

7. Trimmed Current Generation
[Shagun Bhajoria,
MS Thesis, TU Delft]

8. Calibration Methods
1. Sample the output of the error amplifier
2. Simple calibration method
3. Does not impact the direct voltage
[Shagun Bhajoria,
MS Thesis, TU Delft]

9. Unit Calibration circuit
[Shagun Bhajoria,
MS Thesis, TU Delft]

10. Summary to reduce noise
1. Reduce the noise at the source – BGR or external reference voltage.
2. Use a high gain, low input offset Error Amplifier for fast settling and
low noise.
3. Explore the use of Chopper Amplifier to reduce the flicker noise.
4. Use a (RC) filter to reduce the current noise, in the high side current
sensing.
5. Use a (RC) filter in the gate of the current mirror, to reduce the gate
noise voltage.
6. Use trimming resistors / digital controls – less expensive in current
technology.
7. Calibration methods for the same

11. G S Javed, PhD
Analog Design Manager
Founder, King Consultants Education
drgs.javed@gmail.com
Thank you