Search results

This paper proposes a useful pseudo‐logarithmic circuit as a basic building block in the construction of a logarithmic amplifier made from piecewise approximations.

The circuit employs two operational and a handful of resistors, and mimics the logarithmic function over a predefined range. Control of the pseudo‐logarithmic function is achieved by a ratio of resistances defined as x, one of which may be digitally switched, or implemented by tunable transconductors. When controlled by digitally switched resistors, the circuit is particularly attractive because of the commercial availability of such resistors, and with the aid of simple control logic, individual blocks can be algebraically summed to extend the dynamic range of the basic pseudo‐logarithmic block which is 28 dB

Experimental results using off the shelf operational amplifiers (opamps) and a handful of resistors show that the circuit yields a maximum log error of 0.6915 dB for x in (0.22, 4.65).

Proposes a novel circuit capable of realizing the pseudo‐logarithmic function (x−1)/(1+x). The circuit is simple and easily implemented using readily available opamps.

THE idea of a central service and supplies organisation for libraries—a “Library Centre”— such as exist abroad and are described in Library Supply agencies in Europe, is like most ideas in librarianship, not a new one, even taking into account the establishment of Norway's Biblioteksentralen over 60 years ago in 1902, which at that time was called Folkeboksamlingenes Ekspedisjon. This idea, like so so much else, seems to have originated in the fertile brain of Melvil Dewey, taking its final and lasting form as the Library Bureau, established by Dewey himself in 1882.