Digital Signal Processing Reference
In-Depth Information
still small enough to keep using the adopted model for another while yet for some
applications and especially for a better understanding it is more interesting to use a
physical OTFT model that is constructed in accordance with the physical behavior
of the OTFT. At the moment such models are under construction and nice results
have been presented (Oberhoff et al.
2007b
;Lietal.
2010a
,
b
). Nevertheless, for the
simulations in this dissertation those models have not been implemented.
2.7 Other Components
The organic electronics technology presented in this chapter provides p-type organic
transistors. Both the 3-contact and the 4-contact variant have been extensively dis-
cussed in Sects.
2.4.1
and
2.4.2
, respectively. Analog integrated circuits are often
built with more than only transistors: passive components such as resistors, capac-
itors, and inductors are often included in specific analog circuits. Especially in a
unipolar transistor technology those components are a considerable contribution to
the quality of a building block. In this section an overview is given of the feasibility
of making and using passive components in the organic electronics technology.
2.7.1 Resistors
Resistors are often used in analog circuits, e.g., in RC filters. The behavior of an
ideal resistor is described by Ohm's law, given in Eq. (
2.22
). A resistor built in an
integrated circuit technology, though, is a non-ideal component whose behavior must
only match with ideal resistive behavior in the specifications range of interest, e.g.,
the resistive behavior is only required in the frequency band for which the analog
circuit is designed and up to a certain level of bias conditions that are typical for that
analog circuit.
V
=
R
×
I
(2.22)
The applied organic electronics technology does not provide specific layers for mak-
ing resistors. Nevertheless, every material that is present on the wafer has its own
intrinsic resistivity and can be employed as a resistor. The challenge is now to create
resistors that have the desired resistive value, the desired linearity, and the desired
speed. In this section an overview is given of the possible resistor architectures and
their properties.
2.7.1.1 Metal Line Resistor
A first way to make a resistor is a long line of the gold layers that are available in
the technology, as shown in Fig.
2.23
a. The resistance per square of the gold layers
