| 摘要 |
<p>A DVD reading apparatus has a plurality of photodiodes 201 operable to detect light of a specific wavelength reflected from the surface of a DVD. Each photodiode 201 is connected between a positive supply rail and a current mirror arrangement comprising transistors 204, 205, 207 and amplifier 202. The current mirror arrangement is operative to receive an input at the collector of transistor 204 and to generate two outputs identical to the input, a first output at the collector of transistor 205 and a second output at the collector of transistor 207. The first output is connected to an amplification arrangement 206 the output of which is passed to a processing means (not shown) along with the outputs of the amplification arrangements of each other photodiode 201. The second output of each current mirror arrangement, the collector of transistor 207 is output to a common multi-input summing amplifier 209 via an individual buffer arrangement. Each individual buffer arrangement comprises a transistor 221-218, the output being connected to the emitter of said transistor 211-218. The inputs to the common summing amplifier 209 are connected to the collector of each transistor 211-218.</p> |
