TAT7469
Optical TIA Evaluation Board
Introduction
This application note describes how to test a 5 Volt TAT7469
optical TIA evaluation board intended for low noise 1.3 nm
CATV applications over 55 to 1000 MHz.
 EIN typ 3.5 pA/√Hz
 Optical S21Typ 20dB Z/75 dB
For any questions regarding this data or product in general,
please contact: sjcapplication.engineering@tqs.com.
TAT7469 Overview
The TAT7469 is a low noise, low distortion 75 Ohm RF Amplifier which can be configured for either RF or optical TIA
applications. Fabrication on six inch wafers using Triquint's GaAs pHEMT technology results in optimal performance
and cost. The TAT7469 contains two matched amplifiers for push-pull applications. Each amplifier contains on-chip
active biasing. The bias current set point of each amplifier is adjustable with a single resistor from the input to ground.
The TAT7469 dissipates approximately 1.3 W and is assembled in an SOIC-8 package having an exposed backside
paddle. While heat sinking is beneficial, there are no great demands on thermal mounting. The optical TIA evaluation
board is mounted on a large block of aluminum primarily to provide mechanical stability.
TAT7469 Optical TIA Evaluation Board Description
The TAT7469 consists of a pair of low noise amplifiers
that are typically used in a balanced configuration for RF
applications. For optical applications, the input balun is
replaced by a photo detector (PD) applied differentially to
the input of the TAT7469. The photo detector used is a
JDSU EPM 705 with a typical responsitivity of 0.85 A/W
at λ=1300 nm and a capacitance of 0.6 pF at −5 V. Two
peaking inductors provide impedance matching between
the PD capacitance and the TAT7469 inputs. PD bias is
fed via RF chokes with DC blocking on the TAT7469
side. The output is combined by a balun to a 75 ohm F
connector.
The PD is configured in a way to be reverse biased when
+12 V is applied to the diode bias pins with negative
ground. Typical dark current is 16 pA. When 1 mW of
light is applied, the current rises to about 900 uA. The
PD bias is filtered through a low pass network to remove
supply line noise. The PD bias line should be shielded to
mitigate EMI at the high impedance input of the
TAT7469.
The TAT7469 is self biased and should draw approximately 275mA of current when the +5V applied. A resistor divider
is used on the EVB to load Vg at the inputs and in turn modify IDD.
Application Note: Rev. A 07-08-13
© 2013 TriQuint
- 1 of 4 -
Disclaimer: Subject to change without notice
www.triquint.com
TAT7469
Optical TIA Evaluation Board
2
C2
TAT7469 Optical TIA EVB Layout
Evaluation Board TAT7469 Bill of Material
Reference Des.
PCB
U1
Value
Description
Manuf.
Part Number
n/a
TAT7469 Optical EVB PCB
TRIQUINT
1098793 Rev. 1
n/a
TAT7469 Amplifier, SOIC-8
TriQuint
C1, C2
470 pF
CAP, 0402, 10%, 50V, X7R
TDK
C3, C4, C5, C6, C7,
C8, C11, C12, C13,
C14, C17, C22
0.01 uF
CAP, 0402, 10%, 16V, X7R
MURATA
GRM155R71C103KA01D
C9, C10
0.1 uF
CAP, 0603, 10%, 16V, X7R
MURATA
GRM188R71C104KA01D
C22
0.1 uF
CAP, 0603, 10%, 50V, X7R
TDK
R1, R2
2k
RES, 0402, 5%. 1/16W. CHIP
ROHM
R3, R4
TAT7469
ECJ-0EB1H471K
C1608X7R1H104K
MCR01MZPJ202
5.6 k Ω
RES, 0402, 5%. 1/16W. CHIP
VISHAY-DALE
R8
22Ω
RES, 0402, 5%. 1/16W. CHIP
PANASONIC
ERJ-2GEJ220X
R10
100 Ω
RES, 0402, 1%. 1/16W. CHIP
PANASONIC
ERJ-2RKF1000X
R11
0Ω
Thick Film Res, 0402
PANASONIC
ERJ-2GE0R00X
IND, 0805, 5%, 120mA, 11MHz
COILCRAFT
0805LS-273XJLB
L1
27uH
CRCW04025K60FKED
L2, L9
880 nH
IND, 0805, ±5%, Gowanda
GOWANDA
CC0805-880J-2
L4, L8
12 nH
IND, 0402, 5%
COILCRAFT
0402CS-12NXJL
L5, L6
560 nH
IND, 0402, 5%
COILCRAFT
0402AF-561XJL
L7
900 nH
IND, 1008, 10% Ferrite Ind
COILCRAFT
1008AF-901XKL
J1
F connector F-SIDE_GND Conn Precision edge launch
C15, C16, C18, C19,
C20, C21, R5, R6, R7
no load
0402, DNP
T1
1:1 75Ω
TC1-33-75G2+ SMT balun CD542
PD
n/a
Photo Diode EPM705
Mounting Block
n/a
Mounting block for F-Type to optical
Sc440
n/a
4-40, 1/4”, socket head screw
J2-3, J4-5, J6-7
n/a
Conn, 1x2, 0.1 inch 2 pin right angle
Application Note: Rev. A 07-08-13
© 2013 TriQuint
LIGHTHORSE
LTI-FSF55MGT-P-10-A-X7
MINICIRCUITS
TC1-33-75G2+
JDSU
- 2 of 4 -
TRIQUINT
X07051650-004R
1098676
McMaster-CARR 92196A106
MOLEX
022-28-8021
Disclaimer: Subject to change without notice
www.triquint.com
TAT7469
Optical TIA Evaluation Board
TAT7469 Optical TIA EVB Test Setup and Procedure
C10
C4
R6 C16
C14 L6
C8
L1
2
C2
C17
L9
R2
R8
C3
C15 R5
L5 C13
C9
L7
R1
L2
C7
R10
C12
C11
The TAT7469 is designed to operate from a single +5 V supply in conjunction with an on board Photo Detector (PD)
biased at +12 V. Connect the input to a modulated optical source whose bandwidth is 55 to 1 GHz with an optical level
typically a few dBm to -10 dBm or less. Optical input is an SC/APC connector, the output of the EVB is 75 ohms
through a common F connector.






Limit 5V power supply to 300mA for EVB for VDD supply
Limit 12V Power supply to 2mA for PD
Set voltages
Black (-) to Negative Ground
Red (+) to device via choke (PD and IC)
Shielded leads recommended for all supplies - especially PD to avoid EMI pickup.
Apply the following bias. Sequence is not important:
 +5 V at the +VDD terminal (Neg gnd)
 +12V at the DIODE BIAS (Neg gnd)
 IDD BIAS (open) These pins are normally open but can be loaded by a resistor to ground to adjust IDD through
modifying the resistance of a self biased voltage divider on the board.
Turn ON/OFF & Apply RF as needed.
Application Note: Rev. A 07-08-13
© 2013 TriQuint
- 3 of 4 -
Disclaimer: Subject to change without notice
www.triquint.com
TAT7469
Optical TIA Evaluation Board
Performance Plots
Test conditions unless otherwise noted: VDD=+5 V, VPD=+12 V, IDD=248 (ma), Temp.=+25°C
0
30
SN2
S21 vs Optical
25
SN2
S22 vs Optical
‐2
‐4
20
‐6
15
dB
S21 ‐1.25dBm
dB
S21 ‐11.25dBm
10
‐8
S22 ‐1.25dBm
‐10
S22 ‐11.25dBm
‐12
5
‐14
‐16
0
10
210
410
610
810
1010
10
1210
210
410
610
810
1010
1210
MHz
MHz
Optical CSO & CTB (Typical)
Test conditions unless otherwise noted: VDD=+5 V, VPD=+12 V, IDD=248 (ma), Temp.=+25°C,
3.5% OMI, 79 channels NTSC, flat loading
Popt (dBm)
IPD (mA)
Freq. (MHz)
1.4
1.4
1.4
-6
-6
-6
1.33
1.33
1.33
0.24
0.24
0.24
55.25
301.25
547.25
55.25
301.25
547.25
N_floor
(dBm)
-96.9
-95.3
-97.3
-101.1
-100.8
-101.5
Corrected
Fund
Fund (dBm) (dBmV/ch)
-17.4
30.2
-16.6
29.6
-19.1
29.1
-32.1
14.2
-31.5
14.8
-33.8
14.2
CSO_L
(dBc)
-68.7
-68.3
-78.0
CTB (dBc)
-66.2
-64.3
-66.5
-64.3
-63.8
-64.2
CSO_H
(dBc)
-79.2
-71.8
-74.0
Typical CTB presented was limited by the optical transmitter in the test set-up.
Typical EIN Performance
Freq (MHz)
EIN (pA/rtHz)
66
3.9
547
3.7
1000
3.3
Application Note: Rev. A 07-08-13
© 2013 TriQuint
- 4 of 4 -
Disclaimer: Subject to change without notice
www.triquint.com