Nice schematic by dc42 - it graphically reproduced what I described ealirer - sorry that it confused some poster.
The output voltage on the emitter will be the same as the input voltage on the opamp's non-inverting pin.
Howerev, it is not without potential issues:
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You want a base resistor to save-guard the opamp. It also helps with stability should you use a mosfet there.
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For opamps that cannot swing with 07v of the negative rail (gnd in this case), you want to use a darlington or a diode to pad the Vbe. More diodes to pad the Vbe more. This will linit the max positive swing, however.
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As is, the output current is determined by the input voltage + load resistance. To the extent that the load has non-linear v-i characteristics, you can float the load to the collector or introduce a sampling resistor - this type of circuit is often used in a current loop trnasmission.
Hope it helps.