Design techniques and methods to design precision current mirrors, precision current sources. In this work, I have discussed methods to reduce noise and variations in the reference current generation. 1. Negative feedback control 2. Applying filters in the design 3. Calibration 4. Resister Trimming

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