TZA1026T Philips Semiconductors, TZA1026T Datasheet - Page 5
Manufacturer Part Number
Data amplifier and laser supply circuit for CD audio and video optical systems ADALASAuto
The TZA1026 consists of two sections, the RF amplifier
and the automatic laser power control circuit.
The RF amplifier consists of a current input amplifier, an
equalizer/bandwidth section and a transimpedance output
amplifier with an external feedback resistor of 10 k (fixed
1998 Oct 30
Data ampliﬁer and laser supply circuit for CD
audio and video optical systems (ADALASAuto)
Fig.2 Pin configuration.
current output to laser diode
laser supply voltage
external ﬁlter capacitor
laser monitor diode input
central diode input
power-on select input
common mode feedback voltage
external RF feedback resistor
RF ampliﬁer output
gain select input for CD-A/V, CD-R/W
equalizer/speed select input
(n = 1, 2 or 4)
external laser supply gain adjust
The gain of the RF amplifier can be adjusted by the
external input resistors. Fig.3 shows the simplified
schematic which can be used to determine the RF gain.
The signal is AC coupled to the RF amplifier. The formula
to determine the gain is shown below:
The gain can be increased by a factor 4 by making
pin CDRW HIGH. The value of Z
(CDRW = LOW) and 38 k for CD-R/W (CDRW = HIGH).
The equalizer/bandwidth section can be switched between
n = 1, n = 2 (inclusive the corresponding equalizer) or
n = 4 (inclusive the required bandwidth limitation) times
The DC output level of the amplifier can be set by applying
a DC voltage on the common mode feedback pin CMFB.
Since the input signal is AC-coupled the RF output voltage
will swing (symmetrically) around this DC level.
The coupling of the TZA1026 to the signal processor
(SAA7326) can be either AC or DC. When an AC-coupling
is chosen (see Fig.8) the minimum supply voltage can be
applied. When a DC-coupling is chosen (see Fig.9) a
minimum supply voltage of 2.8 V is required.
n is the number of input resistors
R2 is the value of the input resistors( ).
is the RF amplifier gain
is the transimpedance of the amplifier ( )
Fig.3 Simplified schematic.
is 9.8 k for CD-A/V