High-speed operational amplifier evaluation board kitapplication-notes.digchip.com/005/5-11243.pdf · 2009. 2. 8. · high-speed op-amp in SOT23-5 package optimized for high-frequency

High-Speed OperationalAmplifier Evaluation

Board Kit

User Manual

Release 1.0

April 2005

Table of Contents

2/20

Chapter 1: Board descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

SOT23_SINGLE_HF board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3SO8_SINGLE_HF board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4SO8_DUAL_HF board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5SO_S_MULTI board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6SO14_TRIPLE board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Chapter 2: Printed circuit board layout considerations . . . . . . . . . . . . . . . . 8

Chapter 3: Thermal dissipation improvement (SO8_DUAL_HF and SO_S_MULTI boards) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Chapter 4: Power supply bypassing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Chapter 5: Using a single power supply with the SO8_SINGLE board . . . 11

Chapter 6: Channel separation and crosstalk using theSO8_DUAL board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Chapter 7: Output impedance matching and filtering using the SO14_TRIPLE board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Chapter 8: Noise measurement using the SO8_SINGLE_HF board . . . . . . 14

Measurement of the Input Voltage Noise eN . . . . . . . . . . . . . . . . . . . . . . . 15Measurement of the Negative Input Current Noise iNn . . . . . . . . . . . . . . . 15Measurement of the Positive Input Current Noise iNp . . . . . . . . . . . . . . . . 15

Chapter 9: Intermodulation distortion product using theSO8_DUAL board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

User Manual Board descriptions

1 Board descriptions

SOT23_SINGLE_HF boardThis board is provided for the evaluation of a singlehigh-speed op-amp in SOT23-5 packageoptimized for high-frequency signals.

Description of material:

• Two-layer board;

• FR4 (εr=4.6), epoxy 1.6mm

• Copper thickness: 35µm

Figure 1: Electric Schematic of SOT23_SINGLE_HF boardC

810

0nF

/25V

C9

100n

F/2

5V

C6

33uF

/50V

C7

33uF

/50V

1

J4CON1

1

J5CON1

1

J6CON1

+VCC -VCC

J1SMA

J2SMA

R450

R1

R2

R5

50

C4

C2100nF

C3

100nF

+VCC

-VCC

C5

10nF

P1(optional)

C1(optional)

1

5

3

4 2 VC

C-

VC

C+

IC1

TSHXXX

C10

option

3/20

Board descriptions User Manual

SO8_SINGLE_HF boardThis board is provided for the evaluation of asingle high-speed op-amp in SO8 packageoptimized for high-frequency signals.


• Two layers



Figure 2: Electric Schematic of SO8_SINGLE_HF board

J1SMA

J2SMA

R450

R1

R2

R5

50

C4

C2100nF

C3

100nF

+VCC

-VCC

C8

100n

F/2

5V

C9

100n

F/2

5V

C6

33uF

/50V

C7

33uF

/50V

1

J4CON1

1J5CON1

1

J6CON1

+VCC -VCC

C5

100nF6

7

3

2

8

4VCC-

VCC+ /STB1

IC1

TSHXXX

J3SMB

R3

10K

P1(optional)

CV1(optional)

+VCC

C1100nF

IN

OUT

Stby (optional)

4/20


SO8_DUAL_HF boardThis board is provided for the evaluation of adual high-speed op-amp in SO8 packageoptimized for high-frequency signals.


• Two layers



Figure 3: Electric Schematic of SO8_DUAL_HF board

J2SMA

J4SMA

R750

R3

R6

R8

50

C10

C12

100nF

P2(optional)

CV2(optional)

C11100nF

IN2

OUT2

J1SMA

J3SMA

R450

R1

R2

R5

50

C4

C2100nF

C3

100nF

+VCC

-VCC

C5

100nF

P1(optional)

CV1(optional)

C1100nF

IN1

OUT11

8

3

2 4VCC-

VCC+

IC1A

TSHxxx

6

5 7

Epad

IC1BTSHxxx

-VCC

C8

100n

F/2

5V

C9

100n

F/2

5V

C6

33uF

/50V

C7

33uF

/50V

1

J5CON1

1

J6CON1

1

J7CON1

+VCC -VCC

5/20

Board descriptions User Manual

SO_S_MULTI boardThis board is provided for the evaluation of asingle high-speed op-amp in SO8 package in bothinverting and non-inverting configurations, dual orsingle supplies.


• Two layers



Figure 4: Electric Schematic of SO_S_MULTI board

6

7

3

2 4

VC

C-

VC

C+

Epad

IC1TSHxxx

J1SMB

J2SMB

J3SMB

R1 50

R250

R350

R8

R7

R9

R5

R10 R11

C15pF

C11100nF

C9100nF

+VCC1

-VCC1

J4SMB

J5SMB

R450

R14

R15

R16

R18

R17 R19

C17

C13100nF

C10

100nF

+VCC2

-VCC2

C14

1uF

R20

1KR12

R13C16

1nF

C12

100nF

+VCC2

P1

-VCC2

J6SMB

R6

C5

100n

F/2

5V

C6

100n

F/2

5V

C7

CA

PP

C8

CA

PP

1

J10CON1

1

J11CON1

1

J12CON1

+VCC1 -VCC1

C3

100n

F/2

5VC4

100n

F/2

5V

C1

33uF

/50V

C2

33uF

/50V

1

J7CON1

1

J8CON1

1

J9CON1

+VCC2 -VCC2

R21

0R22

0

-VCC1

-VCC2

C19nc

C18nc

C20

100nF

6

7

3

24

VCC-

VCC+81

Epad

IC2TSHxxx

6/20


SO14_TRIPLE boardThis board is provided for the evaluation of a triplehigh-speed op-amp in SO14 with video applicationconsiderations.


• Two layers



Figure 5: Electric Schematic of SO14_TRIPLE board

J3SMB

R150

R8

J9SMB

J6SMB

R4

R9

R7

R10 R11

C19

C4

100nF

C2

100nF

+VCC

-VCC

C1

100nF

C17

100n

F/2

5V

C18

100n

F/2

5V

C15

33uF

/50V

C16

33uF

/50V

1

J11

1

J12

1

J13

+VCC -VCC

C10nc

7

4

5

6

1

11VCC-

VCC+ /STB1

IC1ATSHxxx

C3

100nF

R6

C9nc

R5

+VCC

-VCC

J1SMB

R350

R18

J7SMB

J4SMB

R19

R21

R24

R23 R25

C20

C7

100nF

C14nc

8

10

9

2 /STB2

IC1BTSHxxx

C8

100nF

R22

C13nc

R20

+VCC

-VCC

J2SMB

R250

R26

J8SMB

J5SMB

R12

R27

R16

R15 R17

C21

C5

100nF

C12nc

1412

13

3 /STB3

IC1CTSHxxx

C6

100nF

R14

C11nc

R13

+VCC

-VCC

7/20

Printed circuit board layout considerations User Manual

2 Printed circuit board layout considerations

The use of a proper ground plane on both sides of the PCB is necessary to providelow inductance and a low-resistance common return. The most important factorsaffecting gain flatness and bandwidth are stray capacitance at the output andinverting input. To minimize capacitance, the distance between signal lines and theground plane should be maximized. Feedback component connections must be asshort as possible in order to decrease the associated inductance which affectshigh-frequency gain errors. It is very important to choose the smallest possibleexternal components—for example, surface mounted devices (SMD)—in order tominimize the size of all DC and AC connections. To minimize the effect of trackslength on boards, input and output tracks are 50Ω matched, connected on theboard with a 50Ω resistor as closed as the input and output pins of the amplifier.

Figure 6: Example of layout for high frequency signals using SOT23_SINGLE_HF

GND Ground

Op-amp

50Ω Track 50Ω Track

Low Frequency Power bypass


50Ω Resistor close to the chip50Ω Resistor close to the chip

+ +

Power bypass

Power bypass

Feedback resistor very close to the chip, on the bottom layer to reduce the length of the feedback loop

Bottom layer

Top layer

GND Ground

Op-amp

50Ω Track 50Ω Track



50Ω Resistor close to the chip50Ω Resistor close to the chip

+ +

Power bypass

Power bypass

Feedback resistor very close to the chip, on the bottom layer to reduce the length of the feedback loop

Bottom layer

Top layer

8/20

User Manual Thermal dissipation improvement (SO8_DUAL_HF and SO_S_MULTI boards)

3 Thermal dissipation improvement (SO8_DUAL_HF and SO_S_MULTI boards)

Op-amps can be housed in an Exposed-Pad plastic package. As depicted inFigure 7, this type of package uses a lead frame upon which the die is mounted.The lead frame is exposed as a thermal pad on the underside of the package. Thethermal contact is direct with the dice. This thermal path provides excellent cooling.

The thermal pad is electrically isolated from all pins in the package. It should besoldered to a copper area of the PCB underneath the package. Heat is conductedaway from the package via the thermal paths within this copper area. The copperarea should be connected to (-VCC).

Figure 7: SO8 Exposed-Pad Package

Figure 8: Heat Sink on SO8_DUAL board

Cross Section View

Bottom View

DIC

E

Side View

DICE

1

Cross Section View

Bottom View

DIC

E

Side View

DICE

1

Heat sinkconnectedto -Vcc

Heat sinkconnectedto -Vcc

9/20

Power supply bypassing User Manual

4 Power supply bypassing

Correct power supply bypassing is very important for optimizing performance inhigh-frequency ranges. Bypass capacitors should be placed as close as possibleto the IC pins to improve high-frequency bypassing. A capacitor greater than 1µF isnecessary to minimize the distortion. For better quality bypassing, a capacitor of10nF can be added using the same implementation conditions. Bypass capacitorsmust be incorporated for both the negative and the positive supply.

For example, on the board SO8_SINGLE_HF these capacitors are C6, C7, C8, C9.

Figure 9: Circuit for Power Supply Bypassing

+

-VCC

+VCC

+

TS616

+

-

+

-VCC

+VCC

+

+

-

+

-VCC

+VCC

+

TS616

+

-

+

-VCC

+VCC

+

+

-

10µF

10µF

10nF

10nF

10/20

User Manual Using a single power supply with the SO8_SINGLE board

5 Using a single power supply with the SO8_SINGLE board

The power supply can either be single (12V or 5V referenced to ground) or dual(such as ±6V or ±2.5V).

In the event that a single supply system is used, new biasing is necessary toassume a positive output dynamic range between 0V and +VCC supply rails.Considering the values of VOH and VOL, the amplifier will provide an output dynamicfrom +0.5V to 10.6V on 25Ω load for a 12V supply and from 0.45V to 3.8V on 10Ωload for a 5V supply.

The amplifier must be biased with a mid-supply (nominally +VCC/2), in order tomaintain the DC component of the signal at this value. Several options are possibleto provide this bias supply, such as a virtual ground using an operational amplifieror a two-resistance divider (which is the cheapest solution). A high resistancevalue is required to limit the current consumption. On the other hand, the currentmust be high enough to bias the non-inverting input of the amplifier. If we considerthis bias current (30µA max.) as the 1% of the current through the resistancedivider to keep a stable mid-supply, two resistances of 2.2kΩ can be used in thecase of a 12V power supply and two resistances of 820Ω can be used in the caseof a 5V power supply.

The input provides a high pass filter with a break frequency below 10Hz which isnecessary to remove the original 0 volt DC component of the input signal, and to fixit at +VCC/2.

Figure 10 illustrates a 5V single power supply configuration for the SO8_SINGLEboard.

Figure 10: Circuit for +5V single supply

+

_

RG

IN

+5V

Rfb

10µF

+ 1µF

½ TS616+5V

10nF

CG+

+

_

RG

IN

+5V

Rfb

10µF

+ 1µF

+5V

10nF

CG+

+

_

RG

IN

+5V

Rfb

10µF

+ 1µF

½ TS616+5V

10nF

CG+

+

_

RG

IN

+5V

Rfb

10µF

+ 1µF

+5V

10nF

CG+

+5V

10nF

CG+

Rin=1kΩ

R1820Ω

R2820Ω

11/20

Channel separation and crosstalk using the SO8_DUAL board User Manual

6 Channel separation and crosstalk using the SO8_DUAL board

Figure 11 shows an example of crosstalk of the TSH112. This phenomenon,accentuated at high frequencies, is unavoidable and intrinsic to the circuit itself.

Nevertheless, the PCB layout also has an effect on the crosstalk level. Capacitivecoupling between signal wires, distance between critical signal nodes and powersupply bypassing are the most significant factors.

Figure 11: TSH112 crosstalk using SO8_DUAL board: AV=+2, Rfb=680Ω, Cfb=2pF, RL=100Ω, Vcc=±6V, ±2.5V

10k 100k 1M 10M 100M-100

-80

-60

-40

-20

0

X-T

alk

(dB

)

Frequency (Hz)

12/20

User Manual Output impedance matching and filtering using the SO14_TRIPLE board

7 Output impedance matching and filtering using the SO14_TRIPLE board

The SO14_TRIPLE board allows output impedance matching via a Π resistivenetwork. The aim is to match impedance with the 50Ω input analyzer whilstkeeping the output op-amp load higher than 100Ω.

This Π network can also be used as an output filter. This is useful, for example, inmaking a low-pass third-order filter using a C-L-C configuration—particularlysuitable for video applications.

Figure 12: Output stage on SO14_TRIPLE board

R RR

C C

L

Output with impedancematching using Pi network

Output with LC 3rd orderlow-pass filter

R RR

C C

L

Output with impedancematching using Pi network

Output with LC 3rd orderlow-pass filter

13/20

Noise measurement using the SO8_SINGLE_HF board User Manual

8 Noise measurement using the SO8_SINGLE_HF board

The noise model is shown in Figure 13, where:

• eN: input voltage noise of the amplifier

• iNn: negative input current noise of the amplifier

• iNp: positive input current noise of the amplifier

The thermal noise of a resistance R is:

where ∆F is the specified bandwidth.

On a 1Hz bandwidth the thermal noise is reduced to

where k is the Boltzmann's constant, equal to 1,374.10-23J/°K. T is thetemperature (°K).

The output noise eNo is calculated using the Superposition Theorem. HowevereNo is not the simple sum of all noise sources, but rather the square root of thesum of the square of each noise source, as shown in Equation 1:

Equation 1

Equation 2

Figure 13: Noise Model

+

_

R3

R1

output

R2

iN-

iN+

HP3577Input noise:8nV/√Hz

N1

N2

N3

TS616

eN

+

_

R3

R1

output

R2

iN-

iN+

HP3577Input noise:8nV/√Hz

N1

N2

N3

TS616

eN

4kTR∆F

4kTR

eNo V12

V22

V32

V42

V52

V62

+ + + + +=

eNo2

eN2

g2

iNn2

R22

iNp2

+×+× R32

× g2

× R2R1-------

24kTR1 4kTR2 1 R2

R1-------+

24kTR3×+ +×+=

14/20

User Manual Noise measurement using the SO8_SINGLE_HF board

The input noise of the instrumentation must be extracted from the measured noisevalue. The real output noise value of the driver is:

Equation 3

The input noise is called the Equivalent Input Noise as it is not directly measuredbut is evaluated from the measurement of the output divided by the closed loopgain (eNo/g).

After simplification of the fourth and the fifth term of Equation 2 we obtain:

Equation 4

Measurement of the Input Voltage Noise eNIf we assume a short-circuit on the non-inverting input (R3=0), from Equation 4 wecan derive:

Equation 5

In order to easily extract the value of eN, the resistance R2 will be chosen to be aslow as possible. In the other hand, the gain must be large enough:

R3=0, gain: g=100

Measurement of the Negative Input Current Noise iNnTo measure the negative input current noise iNn, we set R3=0 and use Equation 5.This time the gain must be lower in order to decrease the thermal noisecontribution:

R3=0, gain: g=10

Measurement of the Positive Input Current Noise iNpTo extract iNp from Equation 3, a resistance R3 is connected to the non-invertinginput. The value of R3 must be chosen in order to keep its thermal noisecontribution as low as possible against the iNp contribution:

R3=100Ω, gain: g=10

eNo Measured( )2

instrumentat ion( )2

–=

eNo2

eN2

g2

iNn2

R22

iNp2

+×+× R32× g

2× g 4kTR2 1 R2R1-------+

24kTR3×+×+=

eNo eN2

g2

iNn2

R22

g 4kTR2×+×+×=

15/20

Intermodulation distortion product using the SO8_DUAL board User Manual

9 Intermodulation distortion product using the SO8_DUAL board

Non-ideal output of the amplifier can be described by the following series:

due to non-linearity in the input-output amplitude transfer, where the input isVin=Asinωt, C0 is the DC component, C1(Vin) is the fundamental and Cn

is theamplitude of the harmonics of the output signal Vout.

A one-frequency (one-tone) input signal contributes to harmonic distortion. A two-tone input signal contributes to harmonic distortion and intermodulation product.

The study of the intermodulation and distortion for a two-tone input signal is the firststep in characterizing the driving capability of multi-tone input signals.

In this case:

In the above expression, we can extract distortion terms and intermodulationsterms from a single sine wave: second-order intermodulation terms IM2 by thefrequencies (ω1-ω2) and (ω1+ω2) with an amplitude of C2A2 and third-orderintermodulation terms IM3 by the frequencies (2ω1-ω2), (2ω1+ω2), (−ω1+2ω2) and(ω1+2ω2) with an amplitude of (3/4)C3A3.

We can measure the intermodulation product of the driver by using the driver as amixer via a summing amplifier configuration. In doing this, the non-linearityproblem of an external mixing device is avoided.

Vout C0 C1Vin C2V2

in …CnVn

in+ + +=

( )( )

( )n21

221

21

21in

tsinBtsinACn

....

tsinBtsinA2C

tsinBtsinA1C

0CVout

:then

tsinBtsinAV

ω+ω+

+ω+ω+

ω+ω+=

ω+ω=

16/20

User Manual Intermodulation distortion product using the SO8_DUAL board

Example: TS616 intermodulation measurement using SO8_DUAL board in input/output differential mode.

The following graphs show the IM2 and the IM3 of the TS616 in differentconfigurations. The two-tone input signal was generated by the multi-sourcegenerator Marconi 2026. Each tone has the same amplitude. The measurementwas performed using a HP3585A spectrum analyzer.

Figure 14: Non-inverting Summing Amplifier for intermodulation measurements

Figure 15: Intermodulation vs. Output Amplitude 370kHz & 400kHz, AV=+1.5, Rfb=1kΩ, RL=14Ω diff.,VCC=±2.5V

Vout diff.300Ω

910Ω

+Vcc

100Ω 50Ω

49.9Ω

49.9Ω

1/2TS616

-Vcc

√2:1

1/2TS616

910Ω300Ω

Rout1

Rout2

1kΩ

1kΩ

1kΩ

1kΩ

49.9Ω

49.9Ω

49.9Ω

49.9Ω

50Ω 100Ω

1:√2

50Ω 100Ω

1:√2

Vin1

Vin1

_

+

_

+

Vout diff.300Ω

910Ω

+Vcc

100Ω 50Ω

49.9Ω

49.9Ω

1/2TS616

-Vcc

√2:1

1/2TS616

910Ω300Ω

Rout1

Rout2

1kΩ

1kΩ

1kΩ

1kΩ

49.9Ω

49.9Ω

49.9Ω

49.9Ω

50Ω 100Ω

1:√2

50Ω 100Ω

1:√2

Vin1

Vin1

_

+

_

+

0 1 2 3 4 5 6 7 8-100

-90

-80

-70

-60

-50

-40

-30

IM31140kHz, 1170kHz

IM2770kHz

IM3340kHz, 430kHz

IM230kHz

IM2

and

IM3

(dB

c)

Differential Output Voltage (Vp-p)

17/20

Intermodulation distortion product using the SO8_DUAL board User Manual

Figure 16: Intermodulation vs. Output Amplitude 370kHz & 400kHz, AV=+1.5, Rfb=1kΩ, RL=28Ω diff.,VCC=±2.5V

Figure 17: Intermodulation vs. Output Amplitude 100kHz & 110kHz, AV=+4, Rfb=620Ω, RL=200Ω diff.,VCC=±6V

0 1 2 3 4 5 6 7 8-100

-90

-80

-70

-60

-50

-40

-30

IM31140kHz, 1170kHz

IM2770kHzIM3

340kHz, 430kHzIM230kHz

IM2

and

IM3

(dB

c)


2 4 6 8 10 12 14 16 18 20 22-110

-100

-90

-80

-70

-60

-50

-40

-30

IM3320kHz

IM3310kHz

IM390kHz, 120kHz IM2

210kHz

IM2

and

IM3

(dB

c)


18/20


Figure 18: Intermodulation vs. Output Amplitude 100kHz & 110kHz, AV=+4, Rfb=620Ω, RL=50Ω diff., VCC=±6V

Figure 19: Intermodulation vs. Output Amplitude 370kHz & 400kHz, AV=+4, Rfb=620Ω, RL=200Ω diff.,VCC=±6V

2 4 6 8 10 12 14 16 18 20 22-110

-100

-90

-80

-70

-60

-50

-40

-30

IM390kHz, 120kHz, 310kHz, 320kHz

IM2210kHz

IM2

and

IM3

(dB

c)


0 2 4 6 8 10 12 14 16 18 20 22-110

-100

-90

-80

-70

-60

-50

-40

-30

IM31140kHz, 1170kHz

IM2770kHz

IM3340kHz, 430kHz

IM230kHz

IM2

and

IM3

(dB

c)


19/20


20

Figure 20: Intermodulation vs. Output Amplitude 370kHz & 400kHz, AV=+4, Rfb=620Ω, RL=50Ω diff., VCC=±6V

0 2 4 6 8 10 12 14 16 18 20 22-110

-100

-90

-80

-70

-60

-50

-40

-30

IM31140kHz, 1170kHz

IM2770kHz

IM3340kHz, 430kHz

IM230kHz

IM2

and

IM3

(dB

c)


20/20

Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequencesof use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is grantedby implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subjectto change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are notauthorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics.

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High-speed operational amplifier evaluation board kitapplication-notes.digchip.com/005/5-11243.pdf · 2009. 2. 8. · high-speed op-amp in SOT23-5 package optimized for high-frequency