Thick film printed circuit

A potential dividing circuit comprising a plurality of independent electrode patterns spaced equally between two electrode patterns, and a resistance pattern having uniform width is provided between said two electrode patterns; wherein any one of said plurality of independent patterns is an electrode and another of the remaining independent electrode patterns is adapted to serve as dummy electrodes, whereby exact divided voltage can be obtained.

BACKGROUND OF THE INVENTION 
The present invention relates to a thick film printed circuit formed on a 
ceramic substrate or a printing substrate by printing techniques, and more 
particularly, relates to a thick film printed circuit for dividing 
potentials. 
Most thick film printed circuits have the advantage that relatively exact 
resistance values can be obtained, for the resistance patterns and/or 
electrode patterns are formed by a printing operation which ordinarily 
results in rather high precision. 
However, where at is desired to obtain divided potentials by dividing a 
certain voltage from a resistance of a predetermined fixed value formed by 
printing, the output voltages actually obtained often do not meet those 
theoretically predicted for the circuit. 
SUMMARY OF THE INVENTION 
It is the primary object of the present invention to provide a thick film 
printed circuit including a potential dividing circuit by which any 
desired divided potentials can be obtained accurately. 
It is other object of the present invention to provide a thick film printed 
circuit including a potential dividing circuit which provides 
non-uniformity for the divided potentials. 
It is further other object of the present invention to provide an excellent 
structure of a potential dividing circuit having high performance which 
can be constructed by almost the same printing processes as those 
practiced conventionally.

PREFERRED EMBODIMENT OF THE INVENTION 
FIG. 1 illustrates the construction of a potential dividing circuit formed 
by thick film printed circuit typical of the prior art. 
Conventionally, in order to take up voltage divided from a resistance 
pattern in the thick film printed circuit, as shown in FIG. 1, electrode 
patterns (1) and (3) and an intermediate electrode pattern (2) are printed 
on a ceramnic substrate, a printing substrate or the like, to form a 
desired electrode pattern. Then, on the electrode pattern, an integrated 
resistance pattern consisted of resistance patterns (4) and (5) connected 
to one another is printed to form a potential dividing circuit, wherein 
the desired divided potential can be taken out from the intermediate 
electrode pattern (2). 
However, in such a pattern construction, particularly where the length of 
the resistance pattern (4) is not equal to the length of resistance 
pattern (5), for example, where the length of the resistance pattern (4) 
is longer than that of the resistance pattern (5), i.e. l.sub.1 &gt;l.sub.2, 
the ratio of the divided voltage in actual practice does not always agree 
with the voltage ratio designed at the planning stage. 
The aforementioned disadvantage results when the electrode patterns (1), 
(3) and the intermediate electrode pattern (2) are printed on the 
substrate (6). As shown in FIG. 2, a sloping edge portion (10) is formed 
along the lengths of the electrode patterns, and these sloping edge 
portions have a width of .DELTA.l. The lengths of the resistance patterns 
(4) and (5) thus become shorter by 2.DELTA.l than those lengths would be 
without the sloping edge portions being formed. When the resistance 
patterns are of unequal length, the ratio of these lengths designed at the 
planning stage will thus not likely be maintained. This, of course, alters 
the output potential from its desired value. 
Next, one of the embodiments of the present invention is explained 
referring to FIG. 3. 
The electrode patterns (1), (3) and the intermediate electrode pattern (2) 
are synchronously printed on the substrate (6) to compose a dividing 
potential circuit capable of dividing the input potential by one-third. 
Simultaneously therewhith, another intermediate electrode pattern (8) is 
printed. The desired divided potential is taken out from the intermediate 
electrode pattern (2), and the other intermediate electrode pattern (8) 
remains a dummy electrode. 
In providing a dummy electrode by the intermediate electrode pattern (8) 
between the electrode pattern (1) and the intermdiate electrode pattern 
(2), the sloping edge portions (10) formed at each of the electrode 
patterns has an equal effect on each of the resistance patterns, 
respectively. In other words, it is as follows: 
Consider the length of a resistance pattern (9) formed between the 
electrode patterns (1) and (8) to the l.sub.1, the sum of the widths of 
the sloping edge portions (10) at both ends of the resistance pattern (9) 
to be 2.DELTA.l, the length of the resistance pattern (7) formed between 
the electrode patterns (8) and (2) to be l.sub.4, the length of its 
sloping edge portions (10) to be 2.DELTA.l, the length of the resistance 
pattern (5) formed between the electrode patterns (2) and (3) to be 
l.sub.2 and that of its sloping edge portions (10) to be 2.DELTA.l, the 
ratio of l.sub.3 +l.sub.4 :l.sub.2 =2:1 since the input potential is to be 
divided by one-third. Further, in the case of the width, depth and 
specific electric resistance of each pattern being equal, the resistance 
values of the resistance patterns (5), (7) and (9) are in proportion to 
their length. Accordingly, if it is assumed that the value of input 
voltage is E, and that of output voltage is V, then V can be represented 
by the following expression; 
##EQU1## 
As can be clearly understood from the above represented expression, no 
effect is given by the sloping edge portions (10), which results in 
reducing adverse effects of the sloping edge portions. 
In the embodiment described above, the potential is divided by one-third. 
The potential may also be divided by one-fourth of the input potential by 
providing two intermediate electrode patterns equally spaced between the 
electrode pattern (1) and the intermediate electrode pattern (2) to serve 
as dummy electrodes; and in the case desired to divide potential to 
two-fifths of the input potential, two intermediate electrode patterns 
serving as two dummy electrodes are disposed between the electrode pattern 
(1) and the intermediate electrode pattern (2), and in addition, an 
intermediate electrode pattern serving as a dummy electrode may be 
disposed between the intermediate electrode pattern (2) and the electrode 
pattern (3). 
As described above in detail, if it is desired to divide a certain voltage 
by the ratio of m:n by printed resistance patterns, it is achieved as 
follows; that is, (n+1) of the electrode patterns are provided on the 
substrate, and voltage is applied between the first electrode pattern and 
the (n+1)th electrode pattern, and then voltage is taken out from the 
(n+1-m)th electrode pattern.