Ultrastable Low-Noise Current Amplifiers With Extended Range … · 2017. 3. 7. · •12 G ΩULCA with ±3.6 nA range,

D. Drung and C. Krause

Physikalisch-Technische Bundesanstalt (PTB)Berlin and Braunschweig, Germany

Ultrastable Low -Noise Current Amplifiers With Extended Range and Improved Accuracy

(Ultrastable Low-Noise Current Amplifier → ULCA)

This project has received funding from the European Metrology Programme for Innovation and Research (EMPIR) co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme.

Berlin and Braunschweig, GermanyThanks to ...

PTB colleagues: M. Piepenhagen, M. Luther, M. Götz, E. Pesel, U. Becker, H. Scherer

EU funding: JRP "e-SI-Amp" (15SIB08)

Drung, ULCA, CPEM2016 Mo-61

Outline: - Introduction

- The “standard 3 GΩ ULCA”- Second ULCA generation

- Conclusions

• Realization of ampere based on single-electron transport (SET) current sources→ ISET = 100 pA

• Goal: Measure 100 pA with 10-7 total uncertainty (k = 1, including type B)

2012: Motivation for ULCA development

• Goal: Measure 100 pA with 10 total uncertainty (k = 1, including type B)→ Total uncertainty: 10-17 A = 10 aA = 62 e/s

• Initial approach: CCC with >104 turnsused as current amplifier

• PTB’s CMC entry: 10 ppm standard uncertainty at 100 pA (capacitor charging)

• 1 GΩ standard resistor calibrated with NPL CCC: ≈1 ppm standard uncertainty


used as current amplifier

• SQUID serves as null detector

• Two limitations expected:SQUID nonlinearity & low-frequency noise

33 mm

PTB 14-bit CCC(18276 turns)

New Approach: The ULCA

Basic idea:

• Combine advantages of two technologies: of two technologies: CCC / semiconductor amplifier

• Use CCC for calibration at high current ≈10 nA→ highest accuracy

• Use semiconductor amplifier for measurement at ≈100 pA


for measurement at ≈100 pA→ lowest 1/ f noise→ highest user-friendliness→ series production possible

23 cm

IN

3G 3M

(a) Voltage Output

±44V ±5VOA2OA1

Output = VOUT

Basic ULCA Concept

• Input stage OA1 provides1000-fold current gain

• Thin-film resistor network IN

1MI 1000 I

V

IN IN

IOUTVOUTIRET

Output Signal

IIN

DUT

GND

• Thin-film resistor network with ≈ 3000 chip resistors(much better than thick-film)

• Output stage OA2 performs current-to-voltage conversion

• Voltage output: internal 1 MΩ metal-foil resistor


23 cm

1 MΩ metal-foil resistor→ ATR = VOUT / IIN = 1 GΩ

IN

3G 3M

(a) Voltage Output

±44V ±5VOA2OA1

Output = VOUT

Basic ULCA Concept

• Input stage OA1 provides1000-fold current gain

• Thin-film resistor network IN

1MI 1000 I

V

IN IN

IOUTVOUTIRET

Output Signal

IIN

DUT

GND

• Thin-film resistor network with ≈ 3000 chip resistors(much better than thick-film)

• Output stage OA2 performs current-to-voltage conversion

• Voltage output: internal 1 MΩ metal-foil resistor

(b) Current Output

±44V ±5VOA2OA1

Output = IOUT


1 MΩ metal-foil resistor→ ATR = VOUT / IIN = 1 GΩ

IN

3G 3M

1MI 1000 I

R

±44V ±5V

V

ext

OA2OA1

IRET

IN INIIN

GND IOUTVOUT

Output SignalDUT

• Current output: external resistor Rext = 0 - 100 MΩ(CCC coil or QHR possible)

The “Standard 3 G Ω ULCA”

• Powered by two batteries (one charged while the other used for ULCA supply)→ uninterruptible earth-free battery operation

• Well suited for current measurement & generation or resistance calibration→ Improved instrument for applications with fA to nA currents→ Improved instrument for applications with fA to nA currents

• Current range: ±5 nA @ “normal” mode±5 µA @ “extended” mode (output stage only)

• Excellent accuracy: < 0.1 ppm @ on-site calibration with PTB CCC< 1 ppm @ inter-lab comparisons

• Long-term stability: ≈ 2 ppm/yr @ one year after assembling


≈ 1 ppm/yr @ two years after assembling

• Applications: Calibration of current sources and metersCalibration of high-value resistorsSmall-current travelling standardHigh-accuracy measurements of SET pumps

Calibration of Picoammeter and SourceKeithley 263 current sourceKeithley 6430 picoammeter

Re

lati

ve e

xpa

nd

ed

un

cert

ain

ty (k =

2)

10-5

10-4

10-3

10-2

10-1

11 h

11 h

11 h

3.5 h

300 cycles

300 cycles

300 cycles

100 cycles

Ammeter calibrations (K6430)

CMCs of PTB ('capacitor charging')

CMCs of PTB ('voltage across shunt')

Calibrations with ULCA current source

(3 month calibration interval)

10-5

10-4

10-3

10-2

10-1

5 min

5 min

2 cycles

2 cycles

Current source calibrations (K263)

CMCs of PTB ('voltage across shunt')

Calibrations with ULCA electrometer

(3 month calibration interval)


Re

lati

ve e

xpa

nd

ed

un

cert

ain

ty (

1f 10f

100f 1p 10p

100p 1n 10n

100n 1µ

10-7

10-6

10-53.5 h

3.5 h 1 h

1 h

1 h

1 h100 cycles

100 cycles 30 cycles

30 cycles

30 cycles

30 cycles

Current / A

extended

mode ULCA normal mode extended

1f 10f

100f 1p 10p

100p 1n 10n

100n 1µ

10-7

10-6

10-5

5 min

5 min

5 min

5 min 5 min

2 cycles

2 cycles

2 cycles

2 cycles 2 cycles

Current / A

ULCA normal mode

→ Poster Tu-P20 by H. Scherer (Tuesday 15:00 - 16:00)

High-Accuracy Measurements on SET Pumps

• Two 3 GΩ ULCAs measure ±ISET

• ∆VOUT measured against JVS

103

/ aA

Data from on-off current measurement

White noise 2.3 fA/√Hz

• ∆VOUT measured against JVS → Noise reduced by factor √2 → Influence of DVM negligible

• Uncertainty 0.16 ppm in 21 hours(combined type A & B uncertainty)

• Cable noise ≈ ULCA noise


→ Talk by F. Hohls (We-1 Quantum Standards III on Wednesday 10:30)

102 103 104 105101

102

σ I /

aA

τ / s

Commercial 3 G Ω Variant ULCA -1

• Available fromhttp://www.magnicon.com/metrology/

• Delivered in solid transport box

Single-channel variant

Dual-channel variant

• Delivered in solid transport box with diverse accessory parts(100 MΩ, filter, divider, data logger)

• Includes PTB calibration certificate


Dual-channel variant

Battery box

Second ULCA Generation

The second ULCA generation addresses the following issues:

Improved accuracy at “high” currents• 780 MΩ ULCA with ±50nA range, 0.02 ppm uncertainty → 4.7 fA/√Hz • Secondary standard for ULCA gain calibrations (“CCC replacement”)• Secondary standard for ULCA gain calibrations (“CCC replacement”)• High-accuracy ampere realization for currents below the QHE/CCC range

Improved noise at “low” currents• 12 GΩ ULCA with ±3.6 nA range, < 0.1 ppm uncertainty → 1.3 fA/√Hz• 60 GΩ ULCA with ±0.5 nA range, ≈ 1 ppm uncertainty → 0.7 fA/√Hz• Reduced measurement time / lower uncertainty


Minimum noise and input bias current at “ultralow” currents• 175 GΩ ULCA with ±5 pA range, ≈ 10 ppm uncertainty → 0.43 fA/√Hz• 10 aA uncertainty in 17 minutes, < 100 aA input bias current• Optimized for applications that do not allow current reversal or on/off switching

Improved Direct Current Standard

• Current range < 50 µA

• Two different ULCAs applied10-2

10-1

= 2

)

CMCs: Capacitor charging• Two different ULCAs applied

→ 12 GΩ & 780 MΩ

• Below 50 pA: ULCA cascade→ ATR = 1000×100 MΩ = 100 GΩ

• Above 50 nA: Extended mode

• Reduced uncertainties compared to present CMCs of PTB

10-6

10-5

10-4

10-3

Rel

ativ

e un

cert

aint

y (k

= 2

)

CMCs: Calibrator and shunt,voltage drop across shunt

timely cal.ULCA: quarterly cal.


to present CMCs of PTB

• Performs better than 3 GΩ ULCA 1f 10f 100f 1p 10p 100p 1n 10n 100n 1µ 10µ 100µ 1m 10m10-7

Current (A)

timely cal.

Low -Bias ULCA: Input Bias Stability

24

26

(a)T (

°C)

22

(a)T

0 1 2 3 4 5 6 7 8 9

-40

-20

0

(b)I B,e

ff (

aA)

t (d)

τ = 1 h


t (d)

• No noticeable correlation between IB,eff and T at 10 aA level

• True “attoampere performance”

Low -Bias ULCA: Settling

60

80

100

50 a

A

0

2

4

(pp

m)

0 4 8 12 16 20-20

0

20

40

60

∆Gdy

n (

ppm

)

50 a

A±

4 8 12 16 20

-4

-2

0

∆Gdy

n (

ppm

)t - t0 (s)


• ±5 pA test current generated via 10 GΩ resistor

• Output settles to within ±5 ppm or ±50 aA after ≈ 4 s

0 4 8 12 16 20

t - t0 (s)

Low -Bias ULCA: Cable Noise Measurements

101

102

Cu-PVC coax & St-MgO coax @ 55 mK White noise 0.44 fA/√Hz

(fA

/√H

z)

10-5 10-4 10-3 10-2 10-1 100 10110-1

100

√SI

(fA

/

f (Hz)

103

104

Cu-PVC coax & St-MgO coax @ 55 mK White noise 0.44 fA/√Hz

• Cable combination mounted in


→ Poster Tu-P19 by C. Krause (Tuesday 14:00 - 15:00)10-1 100 101 102 103 104 105

101

102

σ I (

aA)

τ (s)

• Cable combination mounted in dilution fridge with pulse tube

• Total noise 0.44 fA/√Hz @ 55 mK

Conclusions

• ULCA optimized for characterization of SET devices→ 100 pA with 0.1 ppm uncertainty in 7 hours (two 12 G Ω ULCAs)

• Well suited for highly-accurate, traceable current measurement & generation and for resistance calibrationand for resistance calibration→ Improved solution for applications with direct curr ents below 50 µA

• Non-cryogenic and easy-to-use instrument with excellent long-term stability

• Sets new accuracy benchmarks in small-current regime→ Improves state-of-the-art by up to two orders of ma gnitude

• 3 GΩ ULCA commercially available, 2nd generation scheduled for early 2017


http://www.magnicon.com/metrology/

• More information: Drung et al., Rev. Sci. Instrum. 86, 024703 (2015) Drung et al., IEEE Trans. Instrum. Meas. 64, 3021 (2015)Drung et al., Metrologia 52, 756 (2015)Stein et al., Appl. Phys. Lett. 107, 103501 (2015)

Documents

Ultrastable Low-Noise Current Amplifiers With Extended Range … · 2017. 3. 7. · •12 G ΩULCA with ±3.6 nA range,