DatasheetQ Logo
Electronic component search and free download site. Transistors,MosFET ,Diode,Integrated circuits

TZA3043 查看數據表(PDF) - Philips Electronics

零件编号
产品描述 (功能)
生产厂家
TZA3043 Datasheet PDF : 28 Pages
1 2 3 4 5 6 7 8 9 10 Next Last
Philips Semiconductors
Gigabit Ethernet/Fibre Channel
transimpedance amplifier
Product specification
TZA3043; TZA3043B
AGC
The TZA3043 transimpedance amplifier can handle input
currents from 1 µA to 1.5 mA. This means a dynamic
range of 63 dB. At low input currents, the transimpedance
must be high to get enough output voltage, and the noise
should be low enough to guaranty minimum bit error rate.
At high input currents however, the transimpedance
should be low to avoid pulse width distortion. This means
that the gain of the amplifier has to vary depending on the
input signal level to handle such a wide dynamic range.
This is achieved in the TZA3043 by implementing an
Automatic Gain Control (AGC) loop. The AGC loop
consists of a peak detector, a hold capacitor and a gain
control circuit.
The peak amplitude of the signal is detected by the peak
detector and it is stored on the hold capacitor. The voltage
over the hold capacitor is compared to a threshold level.
The threshold level is set to 25 µA (p-p) input current. AGC
becomes active only for input signals larger than the
threshold level.
It is disabled for smaller signals. The transimpedance is
then at its maximum value (8.3 kdifferential).
When AGC is active, the feedback resistor of the
transimpedance amplifier is reduced to keep the output
voltage constant. The transimpedance is regulated from
8.3 kat low currents (I < 30 µA) to 1 kat high currents
(I < 500 µA). Above 500 µA the transimpedance is at its
minimum and can not be reduced further but the front-end
remains linear until input currents of 1.5 mA.
The upper part of Fig.9 shows the output voltages of the
TZA3043 (OUT and OUTQ) as a function of the DC input
current. In the lower part, the difference of both voltages is
shown. It can be seen from the figure that the output
changes linearly up to 25 µA input current where AGC
becomes active. From this point on, AGC tries to keep the
differential output voltage constant around 200 mV for
medium range input currents (input currents <200 µA).
The AGC can not regulate any more above 500 µA input
current and the output voltage rises again with the input
current.
handbVoook3, f.u9ll pagewidth
(V)
3.7
3.5
3.3
3.1
600
Vo(dif)
(mV)
400
200
0
1
Vo(dif) = VOUT VOUTQ.
(1) VCC = 3 V.
(2) VCC = 3.3 V.
(3) VCC = 5 V.
2002 Sep 06
VOUT
MGU105
VCC = 5 V
VOUTQ
(1)
(2)
(3)
10
102
103
104
Ii (µA)
Fig.9 AGC characteristics.
7

Share Link: 

datasheetq.com  [ Privacy Policy ]Request Datasheet ] [ Contact Us ]